diff --git a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/input.js b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/input.js
index 6256942ca5c5..87462c83f603 100644
--- a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/input.js
+++ b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/input.js
@@ -28,9 +28,9 @@ class Foo {
   foo = 0; bar = 1;
 
   #foo;
-  #foo = 1;
-  static #foo;
-  static #foo = Foo.#foo;
+  #foo2 = 1;
+  static #foo3;
+  static #foo4 = Foo.#foo;
 }
 
 class A1 {
diff --git a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/output.js b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/output.js
index 905fe31bdbfb..9970811aabad 100644
--- a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/output.js
+++ b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/output.js
@@ -27,9 +27,9 @@ class Foo {
   foo = 0;
   bar = 1;
   #foo;
-  #foo = 1;
-  static #foo;
-  static #foo = Foo.#foo;
+  #foo2 = 1;
+  static #foo3;
+  static #foo4 = Foo.#foo;
 }
 
 class A1 {
@@ -69,4 +69,4 @@ class A6 {
 class A7 {
   static get static() {}
 
-}
+}
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/types/ClassBody-MethodDefinition/input.js b/packages/babel-generator/test/fixtures/types/ClassBody-MethodDefinition/input.js
index ae3f4b33c003..67ccba8fc28b 100644
--- a/packages/babel-generator/test/fixtures/types/ClassBody-MethodDefinition/input.js
+++ b/packages/babel-generator/test/fixtures/types/ClassBody-MethodDefinition/input.js
@@ -6,13 +6,13 @@ class Foo {
   set foo(bar) {}
 
   async #foo() {}
-  #foo() {}
-  get #foo() {}
-  set #foo(bar) {}
-  * #foo() {}
-  async * #foo() {}
-  get #bar() {}
-  set #baz(taz) {}
+  #foo2() {}
+  get #foo3() {}
+  set #foo3(bar) {}
+  * #foo4() {}
+  async * #foo5() {}
+  get #bar6() {}
+  set #baz6(taz) {}
 
   static async foo() {}
   static foo() {}
@@ -23,13 +23,13 @@ class Foo {
   static * foo() {}
   static async * foo() {}
 
-  static #foo() {}
-  static async #foo() {}
+  static #foo7() {}
+  static async #foo8() {}
   static ["foo"]() {}
-  static get #foo() {}
-  static set #foo(taz) {}
-  static * #foo() {}
-  static async * #foo() {}
+  static get #foo9() {}
+  static set #foo9(taz) {}
+  static * #foo10() {}
+  static async * #foo11() {}
 
   get
   () {}
diff --git a/packages/babel-generator/test/fixtures/types/ClassBody-MethodDefinition/output.js b/packages/babel-generator/test/fixtures/types/ClassBody-MethodDefinition/output.js
index 24f3e9229c84..7f66930a5422 100644
--- a/packages/babel-generator/test/fixtures/types/ClassBody-MethodDefinition/output.js
+++ b/packages/babel-generator/test/fixtures/types/ClassBody-MethodDefinition/output.js
@@ -11,19 +11,19 @@ class Foo {
 
   async #foo() {}
 
-  #foo() {}
+  #foo2() {}
 
-  get #foo() {}
+  get #foo3() {}
 
-  set #foo(bar) {}
+  set #foo3(bar) {}
 
-  *#foo() {}
+  *#foo4() {}
 
-  async *#foo() {}
+  async *#foo5() {}
 
-  get #bar() {}
+  get #bar6() {}
 
-  set #baz(taz) {}
+  set #baz6(taz) {}
 
   static async foo() {}
 
@@ -41,19 +41,19 @@ class Foo {
 
   static async *foo() {}
 
-  static #foo() {}
+  static #foo7() {}
 
-  static async #foo() {}
+  static async #foo8() {}
 
   static ["foo"]() {}
 
-  static get #foo() {}
+  static get #foo9() {}
 
-  static set #foo(taz) {}
+  static set #foo9(taz) {}
 
-  static *#foo() {}
+  static *#foo10() {}
 
-  static async *#foo() {}
+  static async *#foo11() {}
 
   get() {}
 
diff --git a/packages/babel-parser/src/parser/base.js b/packages/babel-parser/src/parser/base.js
index f4fb9f3b66e0..f02e6778270f 100644
--- a/packages/babel-parser/src/parser/base.js
+++ b/packages/babel-parser/src/parser/base.js
@@ -4,12 +4,14 @@ import type { Options } from "../options";
 import type State from "../tokenizer/state";
 import type { PluginsMap } from "./index";
 import type ScopeHandler from "../util/scope";
+import type ClassScopeHandler from "../util/class-scope";
 
 export default class BaseParser {
   // Properties set by constructor in index.js
   options: Options;
   inModule: boolean;
   scope: ScopeHandler<*>;
+  classScope: ClassScopeHandler;
   plugins: PluginsMap;
   filename: ?string;
   sawUnambiguousESM: boolean = false;
diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
index 29ef2ceb3c2f..9d2b74aaaf63 100644
--- a/packages/babel-parser/src/parser/expression.js
+++ b/packages/babel-parser/src/parser/expression.js
@@ -612,15 +612,21 @@ export default class ExpressionParser extends LValParser {
         ? this.parseIdentifier(true)
         : this.parseMaybePrivateName();
       node.computed = computed;
-      if (
-        node.property.type === "PrivateName" &&
-        node.object.type === "Super"
-      ) {
-        this.raise(startPos, "Private fields can't be accessed on super");
+
+      if (node.property.type === "PrivateName") {
+        if (node.object.type === "Super") {
+          this.raise(startPos, "Private fields can't be accessed on super");
+        }
+        this.classScope.usePrivateName(
+          node.property.id.name,
+          node.property.start,
+        );
       }
+
       if (computed) {
         this.expect(tt.bracketR);
       }
+
       if (state.optionalChainMember) {
         node.optional = optional;
         return this.finishNode(node, "OptionalMemberExpression");
diff --git a/packages/babel-parser/src/parser/index.js b/packages/babel-parser/src/parser/index.js
index 681de32d0560..d3f5db419c6b 100644
--- a/packages/babel-parser/src/parser/index.js
+++ b/packages/babel-parser/src/parser/index.js
@@ -7,6 +7,7 @@ import { getOptions } from "../options";
 import StatementParser from "./statement";
 import { SCOPE_ASYNC, SCOPE_PROGRAM } from "../util/scopeflags";
 import ScopeHandler from "../util/scope";
+import ClassScopeHandler from "../util/class-scope";
 
 export type PluginsMap = Map<string, { [string]: any }>;
 
@@ -25,6 +26,7 @@ export default class Parser extends StatementParser {
     this.options = options;
     this.inModule = this.options.sourceType === "module";
     this.scope = new ScopeHandler(this.raise.bind(this), this.inModule);
+    this.classScope = new ClassScopeHandler(this.raise.bind(this));
     this.plugins = pluginsMap(this.options.plugins);
     this.filename = options.sourceFilename;
   }
diff --git a/packages/babel-parser/src/parser/statement.js b/packages/babel-parser/src/parser/statement.js
index be090db6edf9..7a5bc33c9541 100644
--- a/packages/babel-parser/src/parser/statement.js
+++ b/packages/babel-parser/src/parser/statement.js
@@ -20,6 +20,11 @@ import {
   SCOPE_OTHER,
   SCOPE_SIMPLE_CATCH,
   SCOPE_SUPER,
+  CLASS_ELEMENT_OTHER,
+  CLASS_ELEMENT_INSTANCE_GETTER,
+  CLASS_ELEMENT_INSTANCE_SETTER,
+  CLASS_ELEMENT_STATIC_GETTER,
+  CLASS_ELEMENT_STATIC_SETTER,
   type BindingTypes,
 } from "../util/scopeflags";
 
@@ -1171,7 +1176,7 @@ export default class StatementParser extends ExpressionParser {
   }
 
   parseClassBody(constructorAllowsSuper: boolean): N.ClassBody {
-    this.state.classLevel++;
+    this.classScope.enter();
 
     const state = { hadConstructor: false };
     let decorators: N.Decorator[] = [];
@@ -1231,7 +1236,7 @@ export default class StatementParser extends ExpressionParser {
       );
     }
 
-    this.state.classLevel--;
+    this.classScope.exit();
 
     return this.finishNode(classBody, "ClassBody");
   }
@@ -1514,7 +1519,15 @@ export default class StatementParser extends ExpressionParser {
     prop: N.ClassPrivateProperty,
   ) {
     this.expectPlugin("classPrivateProperties", prop.key.start);
-    classBody.body.push(this.parseClassPrivateProperty(prop));
+
+    const node = this.parseClassPrivateProperty(prop);
+    classBody.body.push(node);
+
+    this.classScope.declarePrivateName(
+      node.key.id.name,
+      CLASS_ELEMENT_OTHER,
+      node.key.start,
+    );
   }
 
   pushClassMethod(
@@ -1545,17 +1558,29 @@ export default class StatementParser extends ExpressionParser {
     isAsync: boolean,
   ): void {
     this.expectPlugin("classPrivateMethods", method.key.start);
-    classBody.body.push(
-      this.parseMethod(
-        method,
-        isGenerator,
-        isAsync,
-        /* isConstructor */ false,
-        false,
-        "ClassPrivateMethod",
-        true,
-      ),
+
+    const node = this.parseMethod(
+      method,
+      isGenerator,
+      isAsync,
+      /* isConstructor */ false,
+      false,
+      "ClassPrivateMethod",
+      true,
     );
+    classBody.body.push(node);
+
+    const kind =
+      node.kind === "get"
+        ? node.static
+          ? CLASS_ELEMENT_STATIC_GETTER
+          : CLASS_ELEMENT_INSTANCE_GETTER
+        : node.kind === "set"
+        ? node.static
+          ? CLASS_ELEMENT_STATIC_SETTER
+          : CLASS_ELEMENT_INSTANCE_SETTER
+        : CLASS_ELEMENT_OTHER;
+    this.classScope.declarePrivateName(node.key.id.name, kind, node.key.start);
   }
 
   // Overridden in typescript.js
diff --git a/packages/babel-parser/src/tokenizer/index.js b/packages/babel-parser/src/tokenizer/index.js
index 27f1aaa15f96..a4e2de67a242 100644
--- a/packages/babel-parser/src/tokenizer/index.js
+++ b/packages/babel-parser/src/tokenizer/index.js
@@ -391,14 +391,8 @@ export default class Tokenizer extends LocationParser {
     }
 
     if (
-      (this.hasPlugin("classPrivateProperties") ||
-        this.hasPlugin("classPrivateMethods")) &&
-      this.state.classLevel > 0
-    ) {
-      ++this.state.pos;
-      this.finishToken(tt.hash);
-      return;
-    } else if (
+      this.hasPlugin("classPrivateProperties") ||
+      this.hasPlugin("classPrivateMethods") ||
       this.getPluginOption("pipelineOperator", "proposal") === "smart"
     ) {
       this.finishOp(tt.hash, 1);
diff --git a/packages/babel-parser/src/tokenizer/state.js b/packages/babel-parser/src/tokenizer/state.js
index 874b5cbdfcad..ff0e704b8f00 100644
--- a/packages/babel-parser/src/tokenizer/state.js
+++ b/packages/babel-parser/src/tokenizer/state.js
@@ -77,9 +77,6 @@ export default class State {
   soloAwait: boolean = false;
   inFSharpPipelineDirectBody: boolean = false;
 
-  // Check whether we are in a (nested) class or not.
-  classLevel: number = 0;
-
   // Labels in scope.
   labels: Array<{
     kind: ?("loop" | "switch"),
diff --git a/packages/babel-parser/src/util/class-scope.js b/packages/babel-parser/src/util/class-scope.js
new file mode 100644
index 000000000000..0d1332160a62
--- /dev/null
+++ b/packages/babel-parser/src/util/class-scope.js
@@ -0,0 +1,113 @@
+// @flow
+
+import {
+  CLASS_ELEMENT_KIND_ACCESSOR,
+  CLASS_ELEMENT_FLAG_STATIC,
+  type ClassElementTypes,
+} from "./scopeflags";
+
+export class ClassScope {
+  // A list of private named declared in the current class
+  privateNames: Set<string> = new Set();
+
+  // A list of private getters of setters without their counterpart
+  loneAccessors: Map<string, ClassElementTypes> = new Map();
+
+  // A list of private names used before being defined, mapping to
+  // their position.
+  undefinedPrivateNames: Map<string, number> = new Map();
+}
+
+type raiseFunction = (number, string) => void;
+
+export default class ClassScopeHandler {
+  stack: Array<ClassScope> = [];
+  raise: raiseFunction;
+  undefinedPrivateNames: Map<string, number> = new Map();
+
+  constructor(raise: raiseFunction) {
+    this.raise = raise;
+  }
+
+  current(): ClassScope {
+    return this.stack[this.stack.length - 1];
+  }
+
+  enter() {
+    this.stack.push(new ClassScope());
+  }
+
+  exit() {
+    const oldClassScope = this.stack.pop();
+
+    // Migrate the usage of not yet defined private names to the outer
+    // class scope, or raise an error if we reached the top-level scope.
+
+    const current = this.current();
+
+    // Array.from is needed because this is compiled to an array-like for loop
+    for (const [name, pos] of Array.from(oldClassScope.undefinedPrivateNames)) {
+      if (current) {
+        if (!current.undefinedPrivateNames.has(name)) {
+          current.undefinedPrivateNames.set(name, pos);
+        }
+      } else {
+        this.raiseUndeclaredPrivateName(name, pos);
+      }
+    }
+  }
+
+  declarePrivateName(
+    name: string,
+    elementType: ClassElementTypes,
+    pos: number,
+  ) {
+    const classScope = this.current();
+    let redefined = classScope.privateNames.has(name);
+
+    if (elementType & CLASS_ELEMENT_KIND_ACCESSOR) {
+      const accessor = redefined && classScope.loneAccessors.get(name);
+      if (accessor) {
+        const oldStatic = accessor & CLASS_ELEMENT_FLAG_STATIC;
+        const newStatic = elementType & CLASS_ELEMENT_FLAG_STATIC;
+
+        const oldKind = accessor & CLASS_ELEMENT_KIND_ACCESSOR;
+        const newKind = elementType & CLASS_ELEMENT_KIND_ACCESSOR;
+
+        // The private name can be duplicated only if it is used by
+        // two accessors with different kind (get and set), and if
+        // they have the same placement (static or not).
+        redefined = oldKind === newKind || oldStatic !== newStatic;
+
+        if (!redefined) classScope.loneAccessors.delete(name);
+      } else if (!redefined) {
+        classScope.loneAccessors.set(name, elementType);
+      }
+    }
+
+    if (redefined) {
+      this.raise(pos, `Duplicate private name #${name}`);
+    }
+
+    classScope.privateNames.add(name);
+    classScope.undefinedPrivateNames.delete(name);
+  }
+
+  usePrivateName(name: string, pos: number) {
+    let classScope;
+    for (classScope of this.stack) {
+      if (classScope.privateNames.has(name)) return;
+    }
+
+    if (classScope) {
+      classScope.undefinedPrivateNames.set(name, pos);
+    } else {
+      // top-level
+      this.raiseUndeclaredPrivateName(name, pos);
+    }
+  }
+
+  raiseUndeclaredPrivateName(name: string, pos: number) {
+    this.raise(pos, `Private name #${name} is not defined`);
+  }
+}
diff --git a/packages/babel-parser/src/util/scope.js b/packages/babel-parser/src/util/scope.js
index bc90be4d03cb..1cbf06fb671f 100644
--- a/packages/babel-parser/src/util/scope.js
+++ b/packages/babel-parser/src/util/scope.js
@@ -43,6 +43,7 @@ export default class ScopeHandler<IScope: Scope = Scope> {
   raise: raiseFunction;
   inModule: boolean;
   undefinedExports: Map<string, number> = new Map();
+  undefinedPrivateNames: Map<string, number> = new Map();
 
   constructor(raise: raiseFunction, inModule: boolean) {
     this.raise = raise;
diff --git a/packages/babel-parser/src/util/scopeflags.js b/packages/babel-parser/src/util/scopeflags.js
index d926998835b6..e49359cf615c 100644
--- a/packages/babel-parser/src/util/scopeflags.js
+++ b/packages/babel-parser/src/util/scopeflags.js
@@ -84,3 +84,23 @@ export type BindingTypes =
   | typeof BIND_TS_ENUM
   | typeof BIND_TS_AMBIENT
   | typeof BIND_TS_NAMESPACE;
+
+// prettier-ignore
+export const CLASS_ELEMENT_FLAG_STATIC = 0b1_00,
+             CLASS_ELEMENT_KIND_GETTER = 0b0_10,
+             CLASS_ELEMENT_KIND_SETTER = 0b0_01,
+             CLASS_ELEMENT_KIND_ACCESSOR = CLASS_ELEMENT_KIND_GETTER | CLASS_ELEMENT_KIND_SETTER;
+
+// prettier-ignore
+export const CLASS_ELEMENT_STATIC_GETTER   = CLASS_ELEMENT_KIND_GETTER | CLASS_ELEMENT_FLAG_STATIC,
+             CLASS_ELEMENT_STATIC_SETTER   = CLASS_ELEMENT_KIND_SETTER | CLASS_ELEMENT_FLAG_STATIC,
+             CLASS_ELEMENT_INSTANCE_GETTER = CLASS_ELEMENT_KIND_GETTER,
+             CLASS_ELEMENT_INSTANCE_SETTER = CLASS_ELEMENT_KIND_SETTER,
+             CLASS_ELEMENT_OTHER           = 0;
+
+export type ClassElementTypes =
+  | typeof CLASS_ELEMENT_STATIC_GETTER
+  | typeof CLASS_ELEMENT_STATIC_SETTER
+  | typeof CLASS_ELEMENT_INSTANCE_GETTER
+  | typeof CLASS_ELEMENT_INSTANCE_SETTER
+  | typeof CLASS_ELEMENT_OTHER;
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/README.md b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/README.md
new file mode 100644
index 000000000000..d8f726880604
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/README.md
@@ -0,0 +1,26 @@
+These tests have been generated using the following script:
+
+```js
+var feat = {
+  "field": "#x = 0;",
+  "method": "#x() {}",
+  "get": "get #x() {}",
+  "set": "set #x(_) {}",
+};
+var placement = {
+  "static": "static ",
+  "instance": ""
+}
+
+for (var f1 in feat) for (var f2 in feat) for (var p1 in placement) for (var p2 in placement) {
+  var code = `class A {
+  ${placement[p1]}${feat[f1]}
+  ${placement[p2]}${feat[f2]}
+}`;
+  var name = `${p1}-${f1}-${p2}-${f2}`;
+  var folder = "packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/" + name;
+
+  if (!fs.existsSync(folder)) fs.mkdirSync(folder);
+  fs.writeFileSync(folder + "/input.js", code);
+}
+```
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-field/input.js
new file mode 100644
index 000000000000..bb68229716d6
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = 0;
+  #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-field/output.json
new file mode 100644
index 000000000000..b69a455a0f53
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-field/output.json
@@ -0,0 +1,224 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 31,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 31,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 31,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 31,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 19,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 12,
+                "end": 14,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 13,
+                  "end": 14,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 17,
+                "end": 18,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 22,
+              "end": 29,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 22,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 23,
+                  "end": 24,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 27,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/input.js
new file mode 100644
index 000000000000..95514f1d83fd
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = 0;
+  get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/output.json
new file mode 100644
index 000000000000..62a6d3a10f71
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-get/output.json
@@ -0,0 +1,227 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 35,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 35,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 35,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 35,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 19,
+              "loc": {
+                "start": {
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+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 12,
+                "end": 14,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 13,
+                  "end": 14,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 17,
+                "end": 18,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 22,
+              "end": 33,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 13
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 26,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 6
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 27,
+                  "end": 28,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 31,
+                "end": 33,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/input.js
new file mode 100644
index 000000000000..82fa3236ab43
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = 0;
+  #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/output.json
new file mode 100644
index 000000000000..0d301cbb847c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-method/output.json
@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 31,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 31,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 31,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 31,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 19,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
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+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 12,
+                "end": 14,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
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+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 13,
+                  "end": 14,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 17,
+                "end": 18,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 22,
+              "end": 29,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 22,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 23,
+                  "end": 24,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 27,
+                "end": 29,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 9
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/input.js
new file mode 100644
index 000000000000..4bb80c110229
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = 0;
+  set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/output.json
new file mode 100644
index 000000000000..99af2b8a69a0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-instance-set/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 36,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 36,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 36,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 36,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 19,
+              "loc": {
+                "start": {
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+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 9
+                }
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+              "key": {
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+                "end": 14,
+                "loc": {
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+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 13,
+                  "end": 14,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 17,
+                "end": 18,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 22,
+              "end": 34,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 14
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 26,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 6
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 27,
+                  "end": 28,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 29,
+                  "end": 30,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 9
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 10
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 32,
+                "end": 34,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 12
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 14
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/input.js
new file mode 100644
index 000000000000..67c3cc794ef3
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = 0;
+  static #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/output.json
new file mode 100644
index 000000000000..45ed934caa5d
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-field/output.json
@@ -0,0 +1,224 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 38,
+        "loc": {
+          "start": {
+            "line": 1,
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+                    "identifierName": "x"
+                  },
+                  "name": "x"
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+                "end": 18,
+                "loc": {
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+                  "end": {
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+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
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+              "end": 36,
+              "loc": {
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+                  "line": 3,
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+                },
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+              "static": true,
+              "key": {
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+                "end": 31,
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+                  "loc": {
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+                      "column": 10
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+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
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+                "end": 35,
+                "loc": {
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+        }
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+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/input.js
new file mode 100644
index 000000000000..1f53201d6970
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = 0;
+  static get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/output.json
new file mode 100644
index 000000000000..d4e1a7d1e628
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-get/output.json
@@ -0,0 +1,227 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 42,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 42,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
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+        "start": 0,
+        "end": 42,
+        "loc": {
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+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
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+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 42,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
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+              "end": 19,
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+              "key": {
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+                "end": 14,
+                "loc": {
+                  "start": {
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+                    "column": 2
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+                  "end": {
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+                  "end": 14,
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+                    },
+                    "identifierName": "x"
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+                  "name": "x"
+                }
+              },
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+                "type": "NumericLiteral",
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+                "end": 18,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 8
+                  }
+                },
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+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
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+              "end": 40,
+              "loc": {
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+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 20
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 33,
+                "end": 35,
+                "loc": {
+                  "start": {
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+                    "column": 13
+                  },
+                  "end": {
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+                },
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+                  "end": 35,
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+                    },
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+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 38,
+                "end": 40,
+                "loc": {
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+                  "end": {
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+              }
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+          ]
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+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/input.js
new file mode 100644
index 000000000000..a1229c8992f1
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = 0;
+  static #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/output.json
new file mode 100644
index 000000000000..3fa0178df710
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-method/output.json
@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+        "loc": {
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+            "column": 1
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+        },
+        "id": {
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+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
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+            },
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+          "loc": {
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+            },
+            "end": {
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+              "column": 1
+            }
+          },
+          "body": [
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+              "end": 19,
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+                  "end": 14,
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+                    },
+                    "identifierName": "x"
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+                  "name": "x"
+                }
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+                "end": 18,
+                "loc": {
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+                    "column": 8
+                  }
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+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
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+              "end": 36,
+              "loc": {
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+                  "column": 2
+                },
+                "end": {
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+              },
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+              "key": {
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+                "end": 31,
+                "loc": {
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+                    "column": 9
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 31,
+                  "loc": {
+                    "start": {
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+                      "column": 10
+                    },
+                    "end": {
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+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 36,
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+                  "end": {
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+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/input.js
new file mode 100644
index 000000000000..4221a39406f9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = 0;
+  static set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/output.json
new file mode 100644
index 000000000000..3e3d50633689
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-field-static-set/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 43,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
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+  },
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+    "SyntaxError: Duplicate private name #x (3:13)"
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+  "program": {
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+    "start": 0,
+    "end": 43,
+    "loc": {
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+      }
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+                },
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+              },
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+                "end": 35,
+                "loc": {
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+                  },
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+                  }
+                },
+                "id": {
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+                  "end": 35,
+                  "loc": {
+                    "start": {
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+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
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+                  "end": 37,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 39,
+                "end": 41,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 19
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/input.js
new file mode 100644
index 000000000000..45adc3907e0a
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  get #x() {}
+  #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/output.json
new file mode 100644
index 000000000000..e7c6f5e6bb2e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-field/output.json
@@ -0,0 +1,227 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 35,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 35,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 35,
+        "loc": {
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+            "column": 0
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+          "end": {
+            "line": 4,
+            "column": 1
+          }
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+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 35,
+          "loc": {
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+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
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+              "end": 23,
+              "loc": {
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+                  "column": 2
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+              "key": {
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+                "end": 18,
+                "loc": {
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+                    "column": 6
+                  },
+                  "end": {
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+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 18,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 26,
+              "end": 33,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 26,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 27,
+                  "end": 28,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 31,
+                "end": 32,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/input.js
new file mode 100644
index 000000000000..7818246e3fd0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  get #x() {}
+  get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/output.json
new file mode 100644
index 000000000000..c63e32cca838
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-get/output.json
@@ -0,0 +1,230 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 39,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 39,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 39,
+        "loc": {
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+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
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+          "end": 39,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
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+              "end": 23,
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+                "end": 18,
+                "loc": {
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+                    "column": 6
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 18,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 21,
+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 26,
+              "end": 37,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 13
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 30,
+                "end": 32,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 6
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 31,
+                  "end": 32,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 35,
+                "end": 37,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/input.js
new file mode 100644
index 000000000000..00d50846e973
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  get #x() {}
+  #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/output.json
new file mode 100644
index 000000000000..9fa1c2917097
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-method/output.json
@@ -0,0 +1,229 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 35,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 35,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 35,
+        "loc": {
+          "start": {
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+            "column": 0
+          },
+          "end": {
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+            "column": 1
+          }
+        },
+        "id": {
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+          "end": 7,
+          "loc": {
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+            },
+            "end": {
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+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
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+          "end": 35,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
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+              "end": 23,
+              "loc": {
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+                "start": 16,
+                "end": 18,
+                "loc": {
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+                    "column": 6
+                  },
+                  "end": {
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+                    "column": 8
+                  }
+                },
+                "id": {
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+                  "end": 18,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 21,
+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 26,
+              "end": 33,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 26,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 28,
+                  "loc": {
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+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 33,
+                "loc": {
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+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 9
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-set/input.js
new file mode 100644
index 000000000000..f5b4f4bb8764
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  get #x() {}
+  set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-set/output.json
new file mode 100644
index 000000000000..109fbb70bafe
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-instance-set/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 40,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 40,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 40,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
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+          "end": 7,
+          "loc": {
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+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
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+                "directives": []
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+                  "end": 34,
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+                      "column": 10
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+                }
+              ],
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+                "type": "BlockStatement",
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+                "end": 38,
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+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/input.js
new file mode 100644
index 000000000000..c915535f827c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  get #x() {}
+  static #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/output.json
new file mode 100644
index 000000000000..5c6ec686f516
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-field/output.json
@@ -0,0 +1,227 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 42,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 42,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+        "loc": {
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+            "column": 1
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+          "end": 7,
+          "loc": {
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+              "column": 7
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+          "name": "A"
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+        "body": {
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+          "end": 42,
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+              "column": 8
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+                    "identifierName": "x"
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+                  "name": "x"
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+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
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+                "end": 23,
+                "loc": {
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+                    "column": 11
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+                  "end": {
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+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
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+              "end": 40,
+              "loc": {
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+                "end": {
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+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
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+                "end": 35,
+                "loc": {
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+                  "end": 35,
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+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 38,
+                "end": 39,
+                "loc": {
+                  "start": {
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+                  "raw": "0"
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+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/input.js
new file mode 100644
index 000000000000..88136bae1fe0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  get #x() {}
+  static get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/output.json
new file mode 100644
index 000000000000..65ec3150bbea
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-get/output.json
@@ -0,0 +1,230 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 46,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 46,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+          "end": 7,
+          "loc": {
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+              "column": 1
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+                  "end": 18,
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+                    "end": {
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+                    },
+                    "identifierName": "x"
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+                  "name": "x"
+                }
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+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
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+                "end": 23,
+                "loc": {
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+                  "end": {
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+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
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+              "end": 44,
+              "loc": {
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+                "end": {
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+                  "column": 20
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 37,
+                "end": 39,
+                "loc": {
+                  "start": {
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+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 39,
+                  "loc": {
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+                    },
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+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 44,
+                "loc": {
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+                    "column": 18
+                  },
+                  "end": {
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+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/input.js
new file mode 100644
index 000000000000..73288616ed47
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  get #x() {}
+  static #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/output.json
new file mode 100644
index 000000000000..68c3ff18b28b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-method/output.json
@@ -0,0 +1,229 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 42,
+  "loc": {
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+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
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+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 42,
+    "loc": {
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+        "column": 0
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+      "end": {
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+        "column": 1
+      }
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+    "interpreter": null,
+    "body": [
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+        "loc": {
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+          "end": 7,
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+              "async": false,
+              "params": [],
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+                  }
+                },
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+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
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+              "end": 40,
+              "loc": {
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+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
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+                "end": 35,
+                "loc": {
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+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 38,
+                "end": 40,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/input.js
new file mode 100644
index 000000000000..bce8d6c24669
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  get #x() {}
+  static set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/output.json
new file mode 100644
index 000000000000..470062c22b80
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-get-static-set/output.json
@@ -0,0 +1,248 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 47,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 47,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
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+        "start": 0,
+        "end": 47,
+        "loc": {
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+            "line": 1,
+            "column": 0
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+          "end": {
+            "line": 4,
+            "column": 1
+          }
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+        "id": {
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+          "start": 6,
+          "end": 7,
+          "loc": {
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+              "line": 1,
+              "column": 7
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+          "name": "A"
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+        "body": {
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+          "end": 47,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
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+              "end": 23,
+              "loc": {
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+                "end": {
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+                  "column": 13
+                }
+              },
+              "static": false,
+              "key": {
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+                "end": 18,
+                "loc": {
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+                    "column": 6
+                  },
+                  "end": {
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+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
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+                "end": 23,
+                "loc": {
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+                    "column": 11
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 26,
+              "end": 45,
+              "loc": {
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+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 21
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 37,
+                "end": 39,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 38,
+                  "end": 39,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 40,
+                  "end": 41,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 43,
+                "end": 45,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 19
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/input.js
new file mode 100644
index 000000000000..48e8c322691f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x() {}
+  #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/output.json
new file mode 100644
index 000000000000..d32285dc3ae0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-field/output.json
@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 31,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 31,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
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+        "end": 31,
+        "loc": {
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+            "column": 0
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+            "column": 1
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+        },
+        "id": {
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+          "start": 6,
+          "end": 7,
+          "loc": {
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+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
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+        "body": {
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+          "loc": {
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+              "column": 8
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+            "end": {
+              "line": 4,
+              "column": 1
+            }
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+            {
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+              "end": 19,
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+                  "end": {
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+                    "column": 4
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+                },
+                "id": {
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+                  "end": 14,
+                  "loc": {
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+                      "line": 2,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 9
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 22,
+              "end": 29,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 22,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 23,
+                  "end": 24,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 27,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/input.js
new file mode 100644
index 000000000000..b1d19924d288
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x() {}
+  get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/output.json
new file mode 100644
index 000000000000..8dbf70cdb04b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-get/output.json
@@ -0,0 +1,229 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 35,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 35,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 35,
+        "loc": {
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+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
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+          "start": 6,
+          "end": 7,
+          "loc": {
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+              "column": 6
+            },
+            "end": {
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+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
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+          "end": 35,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
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+              "type": "ClassPrivateMethod",
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+              "end": 19,
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+              "key": {
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+                "start": 12,
+                "end": 14,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
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+                  }
+                },
+                "id": {
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+                  "end": 14,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 17,
+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 9
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 22,
+              "end": 33,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 13
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 26,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 6
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 28,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 31,
+                "end": 33,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/input.js
new file mode 100644
index 000000000000..c1a8a11a361a
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x() {}
+  #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/output.json
new file mode 100644
index 000000000000..7fe8d83f31e1
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-method/output.json
@@ -0,0 +1,228 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 31,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 31,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 31,
+        "loc": {
+          "start": {
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+        }
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+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/input.js
new file mode 100644
index 000000000000..3ac461db7a73
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x() {}
+  set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/output.json
new file mode 100644
index 000000000000..35d6a2f29be3
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-instance-set/output.json
@@ -0,0 +1,247 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 36,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 36,
+    "loc": {
+      "start": {
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+        "column": 0
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+      "end": {
+        "line": 4,
+        "column": 1
+      }
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+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+          "loc": {
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+              "column": 1
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+              "async": false,
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+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/input.js
new file mode 100644
index 000000000000..f9f1b1015567
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x() {}
+  static #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/output.json
new file mode 100644
index 000000000000..8e3500892679
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-field/output.json
@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
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+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
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+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
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+                    "identifierName": "x"
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+                  "name": "x"
+                }
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+              "generator": false,
+              "async": false,
+              "params": [],
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+                "body": [],
+                "directives": []
+              }
+            },
+            {
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+              "end": 36,
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+                }
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+              "static": true,
+              "key": {
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+                "end": 31,
+                "loc": {
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+                  },
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+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 34,
+                "end": 35,
+                "loc": {
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+                  "raw": "0"
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+        }
+      }
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+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/input.js
new file mode 100644
index 000000000000..fdf3bef6984c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x() {}
+  static get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/output.json
new file mode 100644
index 000000000000..1d94cf85460b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-get/output.json
@@ -0,0 +1,229 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 42,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
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+  "program": {
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+    "end": 42,
+    "loc": {
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+              "key": {
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+                "end": 35,
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+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 34,
+                  "end": 35,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 38,
+                "end": 40,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 18
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/input.js
new file mode 100644
index 000000000000..a1aa1d542441
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x() {}
+  static #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/output.json
new file mode 100644
index 000000000000..fd8bc97f5bbd
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-method/output.json
@@ -0,0 +1,228 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 38,
+        "loc": {
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+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 38,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
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+              "end": 19,
+              "loc": {
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+                  "column": 9
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+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 12,
+                "end": 14,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
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+                    "column": 4
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+                "id": {
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+                  "end": 14,
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+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 9
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 22,
+              "end": 36,
+              "loc": {
+                "start": {
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+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 29,
+                "end": 31,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 30,
+                  "end": 31,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 10
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 34,
+                "end": 36,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/input.js
new file mode 100644
index 000000000000..3b2e1e37704a
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x() {}
+  static set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/output.json
new file mode 100644
index 000000000000..b984451082ec
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-method-static-set/output.json
@@ -0,0 +1,247 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 43,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 43,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 43,
+        "loc": {
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+            "column": 0
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+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
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+        "superClass": null,
+        "body": {
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+          "end": 43,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
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+              "column": 1
+            }
+          },
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+              "end": 19,
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+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
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+                "end": 14,
+                "loc": {
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+                    "column": 2
+                  },
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+                  "end": 14,
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+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
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+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
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+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 9
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
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+              "end": 41,
+              "loc": {
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+                  "line": 3,
+                  "column": 21
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 33,
+                "end": 35,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
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+                  "start": 34,
+                  "end": 35,
+                  "loc": {
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+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
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+                  "start": 36,
+                  "end": 37,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 39,
+                "end": 41,
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+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/input.js
new file mode 100644
index 000000000000..095f191f877b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  set #x(_) {}
+  #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/output.json
new file mode 100644
index 000000000000..83b198523bad
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-field/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 36,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 36,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
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+        "end": 36,
+        "loc": {
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+            "column": 0
+          },
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+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
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+          "end": 7,
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+            },
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+          },
+          "name": "A"
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+        "body": {
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+          "end": 36,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
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+              "column": 1
+            }
+          },
+          "body": [
+            {
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+              "end": 24,
+              "loc": {
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+                  "column": 14
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+              },
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+                "end": 18,
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+                }
+              },
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+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 19,
+                  "end": 20,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 9
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 10
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 24,
+                "loc": {
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+                    "line": 2,
+                    "column": 12
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 14
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 27,
+              "end": 34,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
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+                "end": 29,
+                "loc": {
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+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
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+                    "column": 4
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+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 29,
+                  "loc": {
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+                      "column": 3
+                    },
+                    "end": {
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+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 32,
+                "end": 33,
+                "loc": {
+                  "start": {
+                    "line": 3,
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+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "extra": {
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+                  "raw": "0"
+                },
+                "value": 0
+              }
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+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-get/input.js
new file mode 100644
index 000000000000..8e7e5544b96e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  set #x(_) {}
+  get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-get/output.json
new file mode 100644
index 000000000000..08513a3011e8
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-get/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 40,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 40,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
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+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/input.js
new file mode 100644
index 000000000000..f0d912243eef
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  set #x(_) {}
+  #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/output.json
new file mode 100644
index 000000000000..dceb3bd390a6
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-method/output.json
@@ -0,0 +1,247 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 36,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 36,
+    "loc": {
+      "start": {
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+        "column": 0
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+      "end": {
+        "line": 4,
+        "column": 1
+      }
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+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+            "column": 1
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+          "end": 7,
+          "loc": {
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+              }
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+      }
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+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/input.js
new file mode 100644
index 000000000000..d4e2624635cb
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  set #x(_) {}
+  set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/output.json
new file mode 100644
index 000000000000..7add5089ff95
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-instance-set/output.json
@@ -0,0 +1,266 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 41,
+  "loc": {
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+      "column": 0
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+    "end": {
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+      "column": 1
+    }
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+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
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+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 41,
+    "loc": {
+      "start": {
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+        "column": 0
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+      "end": {
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+        "column": 1
+      }
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+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+              "async": false,
+              "params": [
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+              ],
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+                  },
+                  "end": {
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+                    "column": 14
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
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+              "end": 39,
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+                "end": 33,
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+                  },
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+              "params": [
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+              ],
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+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/input.js
new file mode 100644
index 000000000000..3e3b25f208b6
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  set #x(_) {}
+  static #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/output.json
new file mode 100644
index 000000000000..06e380aea7f2
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-field/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 43,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
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+    "end": 43,
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+      }
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+              "column": 1
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+              "end": 24,
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+              },
+              "static": false,
+              "key": {
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+                "end": 18,
+                "loc": {
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+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/input.js
new file mode 100644
index 000000000000..3c0764dfad45
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  set #x(_) {}
+  static get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/output.json
new file mode 100644
index 000000000000..339ca0c0d546
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-get/output.json
@@ -0,0 +1,248 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 47,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
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+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 47,
+    "loc": {
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+        "line": 1,
+        "column": 0
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+      "end": {
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+        "column": 1
+      }
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+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+          "end": 7,
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+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/input.js
new file mode 100644
index 000000000000..ce3a89c61108
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  set #x(_) {}
+  static #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/output.json
new file mode 100644
index 000000000000..184125273236
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-method/output.json
@@ -0,0 +1,247 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 43,
+  "loc": {
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+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 43,
+    "loc": {
+      "start": {
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+        "column": 0
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+      "end": {
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+        "column": 1
+      }
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+    "interpreter": null,
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+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/input.js
new file mode 100644
index 000000000000..7a5e410fdd91
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  set #x(_) {}
+  static set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/output.json
new file mode 100644
index 000000000000..128468f9659f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/instance-set-static-set/output.json
@@ -0,0 +1,266 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 48,
+  "loc": {
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+      "column": 0
+    },
+    "end": {
+      "line": 4,
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+    "end": 48,
+    "loc": {
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+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 41,
+                  "end": 42,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 44,
+                "end": 46,
+                "loc": {
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+                    "line": 3,
+                    "column": 19
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/input.js
new file mode 100644
index 000000000000..3de944035833
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x = 0;
+  #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/output.json
new file mode 100644
index 000000000000..0724b9e565a2
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-field/output.json
@@ -0,0 +1,224 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+        "start": 0,
+        "end": 38,
+        "loc": {
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+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 38,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 26,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 19,
+                "end": 21,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 20,
+                  "end": 21,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 10
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 24,
+                "end": 25,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 15
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 29,
+              "end": 36,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 29,
+                "end": 31,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 30,
+                  "end": 31,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 34,
+                "end": 35,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/input.js
new file mode 100644
index 000000000000..dd34390358ee
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x = 0;
+  get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/output.json
new file mode 100644
index 000000000000..1a3e576e3b80
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-get/output.json
@@ -0,0 +1,227 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 42,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 42,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 42,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 42,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 26,
+              "loc": {
+                "start": {
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+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
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+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 19,
+                "end": 21,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 20,
+                  "end": 21,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 10
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 24,
+                "end": 25,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 15
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 29,
+              "end": 40,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 13
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 33,
+                "end": 35,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 6
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 34,
+                  "end": 35,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 38,
+                "end": 40,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/input.js
new file mode 100644
index 000000000000..ae2b2f980b8a
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x = 0;
+  #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/output.json
new file mode 100644
index 000000000000..d1c2347cb125
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-method/output.json
@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 38,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 38,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 26,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 19,
+                "end": 21,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 20,
+                  "end": 21,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 10
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 24,
+                "end": 25,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 15
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 29,
+              "end": 36,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 29,
+                "end": 31,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 30,
+                  "end": 31,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 34,
+                "end": 36,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 9
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/input.js
new file mode 100644
index 000000000000..8962661873c3
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x = 0;
+  set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/output.json
new file mode 100644
index 000000000000..0a638b426ae2
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-instance-set/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 43,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
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+  "program": {
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+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/input.js
new file mode 100644
index 000000000000..f30eaf46a76c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x = 0;
+  static #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/output.json
new file mode 100644
index 000000000000..7cf03fd42bb7
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-field/output.json
@@ -0,0 +1,224 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 45,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
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+  "program": {
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+    "start": 0,
+    "end": 45,
+    "loc": {
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+        "column": 0
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+      "end": {
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+        "column": 1
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+    "sourceType": "script",
+    "interpreter": null,
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+            "column": 1
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+          "end": 7,
+          "loc": {
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+                "end": 38,
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+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/input.js
new file mode 100644
index 000000000000..27598cc9b1ef
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x = 0;
+  static get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/output.json
new file mode 100644
index 000000000000..98d454b78c67
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-get/output.json
@@ -0,0 +1,227 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 49,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
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+  "program": {
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+    "start": 0,
+    "end": 49,
+    "loc": {
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+        "column": 0
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+          "end": 7,
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+                "end": 25,
+                "loc": {
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+            {
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+              "static": true,
+              "key": {
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+                "end": 42,
+                "loc": {
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+                  },
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+                  "end": 42,
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+                    },
+                    "identifierName": "x"
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+                  "name": "x"
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+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 47,
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+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/input.js
new file mode 100644
index 000000000000..3530aef207c1
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x = 0;
+  static #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/output.json
new file mode 100644
index 000000000000..74c7d35d4fa3
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-method/output.json
@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 45,
+  "loc": {
+    "start": {
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+      "column": 0
+    },
+    "end": {
+      "line": 4,
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+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
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+  "program": {
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+    "loc": {
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+              "loc": {
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+                  "column": 2
+                },
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+                  "line": 3,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 36,
+                "end": 38,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 37,
+                  "end": 38,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 10
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 41,
+                "end": 43,
+                "loc": {
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+                    "line": 3,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/input.js
new file mode 100644
index 000000000000..705e02850f9c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x = 0;
+  static set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/output.json
new file mode 100644
index 000000000000..379ee84d2d94
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-field-static-set/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 50,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 50,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 50,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
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+          "start": 6,
+          "end": 7,
+          "loc": {
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+              "column": 6
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+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 50,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 26,
+              "loc": {
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+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 19,
+                "end": 21,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 2,
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+                  "end": 21,
+                  "loc": {
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+                      "column": 10
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+                    "end": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 24,
+                "end": 25,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 15
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 29,
+              "end": 48,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 21
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 40,
+                "end": 42,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 41,
+                  "end": 42,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 43,
+                  "end": 44,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 46,
+                "end": 48,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 19
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/input.js
new file mode 100644
index 000000000000..5063908de961
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  static get #x() {}
+  #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/output.json
new file mode 100644
index 000000000000..113e8bbbbeeb
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-field/output.json
@@ -0,0 +1,227 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 42,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 42,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 42,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 42,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateMethod",
+              "start": 12,
+              "end": 30,
+              "loc": {
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+                  "column": 2
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+                "end": {
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+                  "column": 20
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 23,
+                "end": 25,
+                "loc": {
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+                    "line": 2,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 24,
+                  "end": 25,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 28,
+                "end": 30,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 18
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 33,
+              "end": 40,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 33,
+                "end": 35,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 34,
+                  "end": 35,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 38,
+                "end": 39,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/input.js
new file mode 100644
index 000000000000..819cf9b38c3c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  static get #x() {}
+  get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/output.json
new file mode 100644
index 000000000000..c7fd9652e864
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-get/output.json
@@ -0,0 +1,230 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 46,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 46,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 46,
+        "loc": {
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+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
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+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 46,
+          "loc": {
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+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
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+              "end": 30,
+              "loc": {
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+                  "column": 2
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+                "end": {
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+                  "column": 20
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 23,
+                "end": 25,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 13
+                  },
+                  "end": {
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+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 24,
+                  "end": 25,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 28,
+                "end": 30,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 18
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 33,
+              "end": 44,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 13
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 37,
+                "end": 39,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 6
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 38,
+                  "end": 39,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 42,
+                "end": 44,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/input.js
new file mode 100644
index 000000000000..e22778f87886
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  static get #x() {}
+  #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/output.json
new file mode 100644
index 000000000000..67e2f41f4ca2
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-method/output.json
@@ -0,0 +1,229 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 42,
+  "loc": {
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+    "SyntaxError: Duplicate private name #x (3:2)"
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+              "async": false,
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+                "end": 35,
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+                }
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+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
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+                "end": 40,
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+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/input.js
new file mode 100644
index 000000000000..21bab2d3e874
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  static get #x() {}
+  set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/output.json
new file mode 100644
index 000000000000..ef06223a73fb
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-instance-set/output.json
@@ -0,0 +1,248 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 47,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 47,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 47,
+        "loc": {
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+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
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+          "end": 7,
+          "loc": {
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+          "end": 47,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
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+              "column": 1
+            }
+          },
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+              "end": 30,
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+                  "column": 20
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+                "end": 25,
+                "loc": {
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+              "async": false,
+              "params": [],
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+                "end": 30,
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+                  },
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+                "directives": []
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+                "end": 39,
+                "loc": {
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+              "kind": "set",
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+              "generator": false,
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+              "params": [
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+                    "end": {
+                      "line": 3,
+                      "column": 10
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 43,
+                "end": 45,
+                "loc": {
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+                  },
+                  "end": {
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+                },
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+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/input.js
new file mode 100644
index 000000000000..70ab10f5eafd
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  static get #x() {}
+  static #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/output.json
new file mode 100644
index 000000000000..e0271651aae5
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-field/output.json
@@ -0,0 +1,227 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 49,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 49,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+            "end": {
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+                },
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+                  "end": 25,
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+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
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+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
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+                "end": 30,
+                "loc": {
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+                  },
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+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
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+              "end": 47,
+              "loc": {
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+                  "column": 2
+                },
+                "end": {
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+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
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+                "end": 42,
+                "loc": {
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+                  },
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+                      "line": 3,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 45,
+                "end": 46,
+                "loc": {
+                  "start": {
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+                  "end": {
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+                    "column": 15
+                  }
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+                  "raw": "0"
+                },
+                "value": 0
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/input.js
new file mode 100644
index 000000000000..dcb23a94a7fa
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  static get #x() {}
+  static get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/output.json
new file mode 100644
index 000000000000..dd680abb9878
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-get/output.json
@@ -0,0 +1,230 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 53,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 53,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+          "end": 7,
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+            },
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+        "body": {
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+          "end": 53,
+          "loc": {
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+            },
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+              "column": 1
+            }
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+          "body": [
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+              "end": 30,
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+              "key": {
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+                "end": 25,
+                "loc": {
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+                    "column": 13
+                  },
+                  "end": {
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+                },
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+                  "end": 25,
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+                    "identifierName": "x"
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+              },
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+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 30,
+                "loc": {
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+                    "line": 2,
+                    "column": 18
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 33,
+              "end": 51,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 20
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 44,
+                "end": 46,
+                "loc": {
+                  "start": {
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+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 46,
+                  "loc": {
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+                      "line": 3,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 49,
+                "end": 51,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 18
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/input.js
new file mode 100644
index 000000000000..5cf7a3e6524f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  static get #x() {}
+  static #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/output.json
new file mode 100644
index 000000000000..297ceb941b4b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-method/output.json
@@ -0,0 +1,229 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 49,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 49,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 49,
+        "loc": {
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+            "column": 0
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+          "end": {
+            "line": 4,
+            "column": 1
+          }
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+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 49,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
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+              "end": 30,
+              "loc": {
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+                  "column": 2
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+                  "column": 20
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 23,
+                "end": 25,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 13
+                  },
+                  "end": {
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+                    "column": 15
+                  }
+                },
+                "id": {
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+                  "start": 24,
+                  "end": 25,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 28,
+                "end": 30,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 18
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 33,
+              "end": 47,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 40,
+                "end": 42,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 41,
+                  "end": 42,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 10
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 45,
+                "end": 47,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-set/input.js
new file mode 100644
index 000000000000..f13a22c0b724
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  static get #x() {}
+  static set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-set/output.json
new file mode 100644
index 000000000000..cb14ff5bd58b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-get-static-set/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 54,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 54,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 54,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
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+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 54,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
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+              "start": 12,
+              "end": 30,
+              "loc": {
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+                  "column": 20
+                }
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+              "static": true,
+              "key": {
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+                "end": 25,
+                "loc": {
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+                  },
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+                      "column": 15
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+                  "name": "x"
+                }
+              },
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+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 28,
+                "end": 30,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 18
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 33,
+              "end": 52,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 21
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 44,
+                "end": 46,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 45,
+                  "end": 46,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 47,
+                  "end": 48,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 50,
+                "end": 52,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 19
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/input.js
new file mode 100644
index 000000000000..2e87605b197c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x() {}
+  #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/output.json
new file mode 100644
index 000000000000..e34c853586a9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-field/output.json
@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 38,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
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+          "end": 38,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateMethod",
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+              "end": 26,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
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+                }
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+              "static": true,
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+                "end": 21,
+                "loc": {
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+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 20,
+                  "end": 21,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 10
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 24,
+                "end": 26,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 29,
+              "end": 36,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 9
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 29,
+                "end": 31,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 30,
+                  "end": 31,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 34,
+                "end": 35,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 8
+                  }
+                },
+                "extra": {
+                  "rawValue": 0,
+                  "raw": "0"
+                },
+                "value": 0
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/input.js
new file mode 100644
index 000000000000..d714c04e0f50
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x() {}
+  get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/output.json
new file mode 100644
index 000000000000..c6b5cb7b3f5b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-get/output.json
@@ -0,0 +1,229 @@
+{
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+  "end": 42,
+  "loc": {
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+      "column": 0
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+      "line": 4,
+      "column": 1
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+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
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+  "program": {
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+    "start": 0,
+    "end": 42,
+    "loc": {
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+        "column": 0
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+        "column": 1
+      }
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+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+          "end": 7,
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+        "body": {
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+            "end": {
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+              "column": 1
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+                "end": 21,
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+                    "identifierName": "x"
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+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
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+                "end": 26,
+                "loc": {
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+                  "end": {
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+                    "column": 16
+                  }
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+                "directives": []
+              }
+            },
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+              "end": 40,
+              "loc": {
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+                "end": {
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+              "static": false,
+              "key": {
+                "type": "PrivateName",
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+                "end": 35,
+                "loc": {
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+                  "end": {
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+              "async": false,
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+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/input.js
new file mode 100644
index 000000000000..520c9088d109
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x() {}
+  #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/output.json
new file mode 100644
index 000000000000..56572b56584e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-method/output.json
@@ -0,0 +1,228 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
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+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+        "loc": {
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+            "column": 1
+          }
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+          "end": 7,
+          "loc": {
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+              "column": 7
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+            "identifierName": "A"
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+        "body": {
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+          "end": 38,
+          "loc": {
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+              "column": 8
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+            "end": {
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+              "column": 1
+            }
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+              "end": 26,
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+                  "column": 16
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+              "key": {
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+                "end": 21,
+                "loc": {
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+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
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+                "end": 26,
+                "loc": {
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+                  "end": {
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+                    "column": 16
+                  }
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+                "directives": []
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+                "end": 31,
+                "loc": {
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+                      "column": 3
+                    },
+                    "end": {
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+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
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+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
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+                "end": 36,
+                "loc": {
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+                    "column": 7
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+                    "line": 3,
+                    "column": 9
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/input.js
new file mode 100644
index 000000000000..b2c76dfa77f4
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x() {}
+  set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/output.json
new file mode 100644
index 000000000000..b8a0773cf4d6
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-instance-set/output.json
@@ -0,0 +1,247 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 43,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 43,
+    "loc": {
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+        "column": 0
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+        "column": 1
+      }
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+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+              "column": 1
+            }
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+              "async": false,
+              "params": [],
+              "body": {
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+                "end": 26,
+                "loc": {
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+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
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+                "end": 35,
+                "loc": {
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+                  },
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+                },
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+                    "end": {
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+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
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+                }
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+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
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+                  "end": 37,
+                  "loc": {
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+                      "line": 3,
+                      "column": 9
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 10
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 39,
+                "end": 41,
+                "loc": {
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+                    "column": 12
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 14
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/input.js
new file mode 100644
index 000000000000..24d63ae53646
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x() {}
+  static #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/output.json
new file mode 100644
index 000000000000..dfaf6f688e1e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-field/output.json
@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 45,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 45,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+            },
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+              "end": 26,
+              "loc": {
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+                  "column": 2
+                },
+                "end": {
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+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
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+                "end": 21,
+                "loc": {
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+                  },
+                  "end": {
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+                },
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+                    },
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+                  },
+                  "name": "x"
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+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
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+                "end": 26,
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+                    "column": 16
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+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 29,
+              "end": 43,
+              "loc": {
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+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
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+                "end": 38,
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+                  "end": 38,
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+                      "column": 10
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+                    "end": {
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+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
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+                "end": 42,
+                "loc": {
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+                    "line": 3,
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+                  "end": {
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+                    "column": 15
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+                "extra": {
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+                  "raw": "0"
+                },
+                "value": 0
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/input.js
new file mode 100644
index 000000000000..8a3c3ff6a962
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x() {}
+  static get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/output.json
new file mode 100644
index 000000000000..e019b3c9aaaa
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-get/output.json
@@ -0,0 +1,229 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 49,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 49,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 49,
+        "loc": {
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+            "column": 0
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+          "end": {
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+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 49,
+          "loc": {
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+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
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+              "end": 26,
+              "loc": {
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+                  "column": 16
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+              "static": true,
+              "key": {
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+                "start": 19,
+                "end": 21,
+                "loc": {
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+                    "line": 2,
+                    "column": 9
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+                  "end": {
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+                  "end": 21,
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+                    },
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+                      "line": 2,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 24,
+                "end": 26,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 29,
+              "end": 47,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 20
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 40,
+                "end": 42,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
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+                  "end": 42,
+                  "loc": {
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+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 47,
+                "loc": {
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+                    "line": 3,
+                    "column": 18
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 20
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/input.js
new file mode 100644
index 000000000000..316f6d89f48f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x() {}
+  static #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/output.json
new file mode 100644
index 000000000000..029d9cd6f8a3
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-method/output.json
@@ -0,0 +1,228 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 45,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 45,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 45,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 45,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateMethod",
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+              "end": 26,
+              "loc": {
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+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 19,
+                "end": 21,
+                "loc": {
+                  "start": {
+                    "line": 2,
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+                  },
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+                  }
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+                  "end": 21,
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+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
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+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 26,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
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+              "end": 43,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 36,
+                "end": 38,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
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+                  "end": 38,
+                  "loc": {
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+                    },
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+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
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+                "start": 41,
+                "end": 43,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/input.js
new file mode 100644
index 000000000000..590b70f3987e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  static #x() {}
+  static set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/output.json
new file mode 100644
index 000000000000..d788eda7fd02
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-method-static-set/output.json
@@ -0,0 +1,247 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 50,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 50,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 50,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 50,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateMethod",
+              "start": 12,
+              "end": 26,
+              "loc": {
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+                  "line": 2,
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+                },
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+              "static": true,
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+                "end": 21,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "end": {
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+                  }
+                },
+                "id": {
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+                  "end": 21,
+                  "loc": {
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+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
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+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 26,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 29,
+              "end": 48,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 21
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 40,
+                "end": 42,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 41,
+                  "end": 42,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 43,
+                  "end": 44,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 46,
+                "end": 48,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 19
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/input.js
new file mode 100644
index 000000000000..315703f68bce
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  static set #x(_) {}
+  #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/output.json
new file mode 100644
index 000000000000..b50939f38415
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-field/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 43,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 43,
+    "loc": {
+      "start": {
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+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+        "end": 43,
+        "loc": {
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+            "column": 1
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+          "end": 7,
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+        "body": {
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+          "end": 43,
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+              "column": 1
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+          "body": [
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+              "generator": false,
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+                  "end": 27,
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+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
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+                }
+              ],
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+                "end": 31,
+                "loc": {
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+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
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+              "end": 41,
+              "loc": {
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+                "end": 36,
+                "loc": {
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+                  },
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+                    "end": {
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+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start": 39,
+                "end": 40,
+                "loc": {
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+                    "line": 3,
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+                  "end": {
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+                  "raw": "0"
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+              }
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+        }
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+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/input.js
new file mode 100644
index 000000000000..b2515ac17405
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  static set #x(_) {}
+  get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/output.json
new file mode 100644
index 000000000000..ddea1a756790
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-get/output.json
@@ -0,0 +1,248 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 47,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 47,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 47,
+        "loc": {
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+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
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+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
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+          "end": 47,
+          "loc": {
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+              "column": 8
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+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
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+              "end": 31,
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+              "generator": false,
+              "async": false,
+              "params": [
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+                  "end": 27,
+                  "loc": {
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+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
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+                "end": 31,
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+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
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+              "end": 45,
+              "loc": {
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+                  "column": 2
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+                  "column": 13
+                }
+              },
+              "static": false,
+              "key": {
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+                "end": 40,
+                "loc": {
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+                    "line": 3,
+                    "column": 6
+                  },
+                  "end": {
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+                    "column": 8
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 39,
+                  "end": 40,
+                  "loc": {
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+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 8
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "get",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 43,
+                "end": 45,
+                "loc": {
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+                    "line": 3,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 13
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/input.js
new file mode 100644
index 000000000000..8249487ab52e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  static set #x(_) {}
+  #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/output.json
new file mode 100644
index 000000000000..3b9334d91225
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-method/output.json
@@ -0,0 +1,247 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 43,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 43,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+        "loc": {
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+            "column": 1
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+          "end": 7,
+          "loc": {
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+            },
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+          "end": 43,
+          "loc": {
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+              "column": 8
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+            "end": {
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+              "column": 1
+            }
+          },
+          "body": [
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+              "end": 31,
+              "loc": {
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+                "end": 25,
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+                  "end": 27,
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+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
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+                "end": 31,
+                "loc": {
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+                  },
+                  "end": {
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+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
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+              "end": 41,
+              "loc": {
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+                },
+                "end": {
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+              },
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+              "key": {
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+                "end": 36,
+                "loc": {
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+                  },
+                  "end": {
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+                },
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+                  "end": 36,
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+                }
+              },
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+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
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+                "end": 41,
+                "loc": {
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+                  },
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+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/input.js
new file mode 100644
index 000000000000..3b7d8653ee40
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  static set #x(_) {}
+  set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/output.json
new file mode 100644
index 000000000000..b56cf90f93db
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-instance-set/output.json
@@ -0,0 +1,266 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 48,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 48,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
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+        "end": 48,
+        "loc": {
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+        },
+        "id": {
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+          "end": 7,
+          "loc": {
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+            },
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+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
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+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/input.js
new file mode 100644
index 000000000000..3dfbfe2861d4
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  static set #x(_) {}
+  static #x = 0;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/output.json
new file mode 100644
index 000000000000..c063c6722c93
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-field/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 50,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
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+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:9)"
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+  "program": {
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+    "start": 0,
+    "end": 50,
+    "loc": {
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+                "directives": []
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+                "end": 47,
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\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-get/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-get/input.js
new file mode 100644
index 000000000000..5ac842d7dc2f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-get/input.js
@@ -0,0 +1,4 @@
+class A {
+  static set #x(_) {}
+  static get #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-get/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-get/output.json
new file mode 100644
index 000000000000..06b5a7c528b0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-get/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 54,
+  "loc": {
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+      "column": 0
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+      "line": 4,
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+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 54,
+    "loc": {
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+        "column": 0
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+                "directives": []
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+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/input.js
new file mode 100644
index 000000000000..3f3537bcb0a0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/input.js
@@ -0,0 +1,4 @@
+class A {
+  static set #x(_) {}
+  static #x() {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/output.json
new file mode 100644
index 000000000000..78b17369506f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-method/output.json
@@ -0,0 +1,247 @@
+{
+  "type": "File",
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+    "start": 0,
+    "end": 50,
+    "loc": {
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+              "end": 48,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 41,
+                "end": 43,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 11
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 42,
+                  "end": 43,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 10
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 11
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 46,
+                "end": 48,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 14
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 16
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/input.js
new file mode 100644
index 000000000000..d6337e16b74f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/input.js
@@ -0,0 +1,4 @@
+class A {
+  static set #x(_) {}
+  static set #x(_) {}
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/options.json
new file mode 100644
index 000000000000..af02072af9d9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties", "classPrivateMethods"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/output.json
new file mode 100644
index 000000000000..146f1c39f34d
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-names-duplicated/static-set-static-set/output.json
@@ -0,0 +1,266 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 55,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Duplicate private name #x (3:13)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 55,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 55,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 55,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateMethod",
+              "start": 12,
+              "end": 31,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 21
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 23,
+                "end": 25,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 24,
+                  "end": 25,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 26,
+                  "end": 27,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 29,
+                "end": 31,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 19
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateMethod",
+              "start": 34,
+              "end": 53,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 21
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "PrivateName",
+                "start": 45,
+                "end": 47,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 15
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 46,
+                  "end": 47,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "computed": false,
+              "kind": "set",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [
+                {
+                  "type": "Identifier",
+                  "start": 48,
+                  "end": 49,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 17
+                    },
+                    "identifierName": "_"
+                  },
+                  "name": "_"
+                }
+              ],
+              "body": {
+                "type": "BlockStatement",
+                "start": 51,
+                "end": 53,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 19
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 21
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/input.js
new file mode 100644
index 000000000000..e4e3ae4c3870
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/input.js
@@ -0,0 +1,9 @@
+class B {
+  meth() {
+    class A {
+      #x = this.#y;
+    }
+  }
+
+  #y;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/options.json
new file mode 100644
index 000000000000..25819769bb20
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/output.json
new file mode 100644
index 000000000000..1bd1092fae92
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-outer-class/output.json
@@ -0,0 +1,352 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 73,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 9,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 73,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 9,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 73,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 9,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "B"
+          },
+          "name": "B"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 73,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 9,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start": 12,
+              "end": 64,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 6,
+                  "column": 3
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start": 12,
+                "end": 16,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 6
+                  },
+                  "identifierName": "meth"
+                },
+                "name": "meth"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 19,
+                "end": 64,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 6,
+                    "column": 3
+                  }
+                },
+                "body": [
+                  {
+                    "type": "ClassDeclaration",
+                    "start": 25,
+                    "end": 60,
+                    "loc": {
+                      "start": {
+                        "line": 3,
+                        "column": 4
+                      },
+                      "end": {
+                        "line": 5,
+                        "column": 5
+                      }
+                    },
+                    "id": {
+                      "type": "Identifier",
+                      "start": 31,
+                      "end": 32,
+                      "loc": {
+                        "start": {
+                          "line": 3,
+                          "column": 10
+                        },
+                        "end": {
+                          "line": 3,
+                          "column": 11
+                        },
+                        "identifierName": "A"
+                      },
+                      "name": "A"
+                    },
+                    "superClass": null,
+                    "body": {
+                      "type": "ClassBody",
+                      "start": 33,
+                      "end": 60,
+                      "loc": {
+                        "start": {
+                          "line": 3,
+                          "column": 12
+                        },
+                        "end": {
+                          "line": 5,
+                          "column": 5
+                        }
+                      },
+                      "body": [
+                        {
+                          "type": "ClassPrivateProperty",
+                          "start": 41,
+                          "end": 54,
+                          "loc": {
+                            "start": {
+                              "line": 4,
+                              "column": 6
+                            },
+                            "end": {
+                              "line": 4,
+                              "column": 19
+                            }
+                          },
+                          "static": false,
+                          "key": {
+                            "type": "PrivateName",
+                            "start": 41,
+                            "end": 43,
+                            "loc": {
+                              "start": {
+                                "line": 4,
+                                "column": 6
+                              },
+                              "end": {
+                                "line": 4,
+                                "column": 8
+                              }
+                            },
+                            "id": {
+                              "type": "Identifier",
+                              "start": 42,
+                              "end": 43,
+                              "loc": {
+                                "start": {
+                                  "line": 4,
+                                  "column": 7
+                                },
+                                "end": {
+                                  "line": 4,
+                                  "column": 8
+                                },
+                                "identifierName": "x"
+                              },
+                              "name": "x"
+                            }
+                          },
+                          "value": {
+                            "type": "MemberExpression",
+                            "start": 46,
+                            "end": 53,
+                            "loc": {
+                              "start": {
+                                "line": 4,
+                                "column": 11
+                              },
+                              "end": {
+                                "line": 4,
+                                "column": 18
+                              }
+                            },
+                            "object": {
+                              "type": "ThisExpression",
+                              "start": 46,
+                              "end": 50,
+                              "loc": {
+                                "start": {
+                                  "line": 4,
+                                  "column": 11
+                                },
+                                "end": {
+                                  "line": 4,
+                                  "column": 15
+                                }
+                              }
+                            },
+                            "property": {
+                              "type": "PrivateName",
+                              "start": 51,
+                              "end": 53,
+                              "loc": {
+                                "start": {
+                                  "line": 4,
+                                  "column": 16
+                                },
+                                "end": {
+                                  "line": 4,
+                                  "column": 18
+                                }
+                              },
+                              "id": {
+                                "type": "Identifier",
+                                "start": 52,
+                                "end": 53,
+                                "loc": {
+                                  "start": {
+                                    "line": 4,
+                                    "column": 17
+                                  },
+                                  "end": {
+                                    "line": 4,
+                                    "column": 18
+                                  },
+                                  "identifierName": "y"
+                                },
+                                "name": "y"
+                              }
+                            },
+                            "computed": false
+                          }
+                        }
+                      ]
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 68,
+              "end": 71,
+              "loc": {
+                "start": {
+                  "line": 8,
+                  "column": 2
+                },
+                "end": {
+                  "line": 8,
+                  "column": 5
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 68,
+                "end": 70,
+                "loc": {
+                  "start": {
+                    "line": 8,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 8,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 69,
+                  "end": 70,
+                  "loc": {
+                    "start": {
+                      "line": 8,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 8,
+                      "column": 4
+                    },
+                    "identifierName": "y"
+                  },
+                  "name": "y"
+                }
+              },
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/input.js
new file mode 100644
index 000000000000..bd7c6a515696
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/input.js
@@ -0,0 +1,4 @@
+class A {
+  #x = this.#y;
+  #y;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/options.json
new file mode 100644
index 000000000000..25819769bb20
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties"]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/output.json
new file mode 100644
index 000000000000..3c7ad5de9321
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/declared-later-same-class/output.json
@@ -0,0 +1,245 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 33,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 4,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 33,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 4,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 33,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 4,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 33,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 4,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 25,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 15
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 12,
+                "end": 14,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 13,
+                  "end": 14,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "MemberExpression",
+                "start": 17,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 7
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 14
+                  }
+                },
+                "object": {
+                  "type": "ThisExpression",
+                  "start": 17,
+                  "end": 21,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 7
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 11
+                    }
+                  }
+                },
+                "property": {
+                  "type": "PrivateName",
+                  "start": 22,
+                  "end": 24,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 12
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 14
+                    }
+                  },
+                  "id": {
+                    "type": "Identifier",
+                    "start": 23,
+                    "end": 24,
+                    "loc": {
+                      "start": {
+                        "line": 2,
+                        "column": 13
+                      },
+                      "end": {
+                        "line": 2,
+                        "column": 14
+                      },
+                      "identifierName": "y"
+                    },
+                    "name": "y"
+                  }
+                },
+                "computed": false
+              }
+            },
+            {
+              "type": "ClassPrivateProperty",
+              "start": 28,
+              "end": 31,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 3,
+                  "column": 5
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 28,
+                "end": 30,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 29,
+                  "end": 30,
+                  "loc": {
+                    "start": {
+                      "line": 3,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 3,
+                      "column": 4
+                    },
+                    "identifierName": "y"
+                  },
+                  "name": "y"
+                }
+              },
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/input.js
new file mode 100644
index 000000000000..3177068d7eb0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/input.js
@@ -0,0 +1,6 @@
+class A {
+  #x;
+  meth() {
+    var prop = foo.#priv;
+  }
+}
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/options.json
new file mode 100644
index 000000000000..1ca5069a3a2f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/options.json
@@ -0,0 +1,5 @@
+{
+  "plugins": [
+    "classPrivateProperties"
+  ]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/output.json
new file mode 100644
index 000000000000..f13ed5f0567c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-nested/output.json
@@ -0,0 +1,309 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 58,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 6,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Private name #priv is not defined (4:19)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 58,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 6,
+        "column": 1
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 58,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 6,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 58,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 6,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 15,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 5
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 12,
+                "end": 14,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 4
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 13,
+                  "end": 14,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 4
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              "value": null
+            },
+            {
+              "type": "ClassMethod",
+              "start": 18,
+              "end": 56,
+              "loc": {
+                "start": {
+                  "line": 3,
+                  "column": 2
+                },
+                "end": {
+                  "line": 5,
+                  "column": 3
+                }
+              },
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start": 18,
+                "end": 22,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 3,
+                    "column": 6
+                  },
+                  "identifierName": "meth"
+                },
+                "name": "meth"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 25,
+                "end": 56,
+                "loc": {
+                  "start": {
+                    "line": 3,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 5,
+                    "column": 3
+                  }
+                },
+                "body": [
+                  {
+                    "type": "VariableDeclaration",
+                    "start": 31,
+                    "end": 52,
+                    "loc": {
+                      "start": {
+                        "line": 4,
+                        "column": 4
+                      },
+                      "end": {
+                        "line": 4,
+                        "column": 25
+                      }
+                    },
+                    "declarations": [
+                      {
+                        "type": "VariableDeclarator",
+                        "start": 35,
+                        "end": 51,
+                        "loc": {
+                          "start": {
+                            "line": 4,
+                            "column": 8
+                          },
+                          "end": {
+                            "line": 4,
+                            "column": 24
+                          }
+                        },
+                        "id": {
+                          "type": "Identifier",
+                          "start": 35,
+                          "end": 39,
+                          "loc": {
+                            "start": {
+                              "line": 4,
+                              "column": 8
+                            },
+                            "end": {
+                              "line": 4,
+                              "column": 12
+                            },
+                            "identifierName": "prop"
+                          },
+                          "name": "prop"
+                        },
+                        "init": {
+                          "type": "MemberExpression",
+                          "start": 42,
+                          "end": 51,
+                          "loc": {
+                            "start": {
+                              "line": 4,
+                              "column": 15
+                            },
+                            "end": {
+                              "line": 4,
+                              "column": 24
+                            }
+                          },
+                          "object": {
+                            "type": "Identifier",
+                            "start": 42,
+                            "end": 45,
+                            "loc": {
+                              "start": {
+                                "line": 4,
+                                "column": 15
+                              },
+                              "end": {
+                                "line": 4,
+                                "column": 18
+                              },
+                              "identifierName": "foo"
+                            },
+                            "name": "foo"
+                          },
+                          "property": {
+                            "type": "PrivateName",
+                            "start": 46,
+                            "end": 51,
+                            "loc": {
+                              "start": {
+                                "line": 4,
+                                "column": 19
+                              },
+                              "end": {
+                                "line": 4,
+                                "column": 24
+                              }
+                            },
+                            "id": {
+                              "type": "Identifier",
+                              "start": 47,
+                              "end": 51,
+                              "loc": {
+                                "start": {
+                                  "line": 4,
+                                  "column": 20
+                                },
+                                "end": {
+                                  "line": 4,
+                                  "column": 24
+                                },
+                                "identifierName": "priv"
+                              },
+                              "name": "priv"
+                            }
+                          },
+                          "computed": false
+                        }
+                      }
+                    ],
+                    "kind": "var"
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/input.js b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/input.js
new file mode 100644
index 000000000000..10607b89b6db
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/input.js
@@ -0,0 +1 @@
+var prop = foo.#priv;
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/options.json b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/options.json
new file mode 100644
index 000000000000..1ca5069a3a2f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/options.json
@@ -0,0 +1,5 @@
+{
+  "plugins": [
+    "classPrivateProperties"
+  ]
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/output.json b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/output.json
new file mode 100644
index 000000000000..88c45d101fa8
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/experimental/class-private-properties/undeclared-top-level/output.json
@@ -0,0 +1,153 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 21,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 21
+    }
+  },
+  "errors": [
+    "SyntaxError: Private name #priv is not defined (1:15)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 21,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 21
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "VariableDeclaration",
+        "start": 0,
+        "end": 21,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 21
+          }
+        },
+        "declarations": [
+          {
+            "type": "VariableDeclarator",
+            "start": 4,
+            "end": 20,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 4
+              },
+              "end": {
+                "line": 1,
+                "column": 20
+              }
+            },
+            "id": {
+              "type": "Identifier",
+              "start": 4,
+              "end": 8,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 4
+                },
+                "end": {
+                  "line": 1,
+                  "column": 8
+                },
+                "identifierName": "prop"
+              },
+              "name": "prop"
+            },
+            "init": {
+              "type": "MemberExpression",
+              "start": 11,
+              "end": 20,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 11
+                },
+                "end": {
+                  "line": 1,
+                  "column": 20
+                }
+              },
+              "object": {
+                "type": "Identifier",
+                "start": 11,
+                "end": 14,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 14
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "property": {
+                "type": "PrivateName",
+                "start": 15,
+                "end": 20,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 15
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 20
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 16,
+                  "end": 20,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 16
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 20
+                    },
+                    "identifierName": "priv"
+                  },
+                  "name": "priv"
+                }
+              },
+              "computed": false
+            }
+          }
+        ],
+        "kind": "var"
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/get-get/options.json b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/get-get/options.json
index 9c0ba0e4b46a..49dcfc816842 100644
--- a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/get-get/options.json
+++ b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/get-get/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Duplicate private field"
+  "throws": "Duplicate private name #getSet"
 }
diff --git a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/get-method/options.json b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/get-method/options.json
index 9c0ba0e4b46a..1edb048c1285 100644
--- a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/get-method/options.json
+++ b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/get-method/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Duplicate private field"
+  "throws": "Duplicate private name #foo"
 }
diff --git a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-get/options.json b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-get/options.json
index 9c0ba0e4b46a..1edb048c1285 100644
--- a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-get/options.json
+++ b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-get/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Duplicate private field"
+  "throws": "Duplicate private name #foo"
 }
diff --git a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-method/options.json b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-method/options.json
index 9c0ba0e4b46a..b3e2e5dade0d 100644
--- a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-method/options.json
+++ b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-method/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Duplicate private field"
+  "throws": "Duplicate private name #dank"
 }
diff --git a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-set/options.json b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-set/options.json
index 9c0ba0e4b46a..1edb048c1285 100644
--- a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-set/options.json
+++ b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/method-set/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Duplicate private field"
+  "throws": "Duplicate private name #foo"
 }
diff --git a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/set-method/options.json b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/set-method/options.json
index 9c0ba0e4b46a..1edb048c1285 100644
--- a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/set-method/options.json
+++ b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/set-method/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Duplicate private field"
+  "throws": "Duplicate private name #foo"
 }
diff --git a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/set-set/options.json b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/set-set/options.json
index 9c0ba0e4b46a..49dcfc816842 100644
--- a/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/set-set/options.json
+++ b/packages/babel-plugin-proposal-private-methods/test/fixtures/duplicated-names/set-set/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Duplicate private field"
+  "throws": "Duplicate private name #getSet"
 }
diff --git a/scripts/parser-tests/flow/whitelist.txt b/scripts/parser-tests/flow/whitelist.txt
index 8e24ebf0a28d..668fb625d47d 100644
--- a/scripts/parser-tests/flow/whitelist.txt
+++ b/scripts/parser-tests/flow/whitelist.txt
@@ -14,10 +14,4 @@ export_import_reserved_words/migrated_0003.js
 export_statements/export_trailing_comma.js
 nullish_coalescing/precedence_and.js
 nullish_coalescing/precedence_or.js
-private_class_properties/getter_and_field.js
-private_class_properties/getter_duplicate.js
-private_class_properties/multiple.js
-private_class_properties/multiple.js
-private_class_properties/setter_and_field.js
-private_class_properties/setter_duplicate.js
 types/member/reserved_words.js
diff --git a/scripts/parser-tests/test262/whitelist.txt b/scripts/parser-tests/test262/whitelist.txt
index 512bee9a2ca8..d7a38c2104cf 100644
--- a/scripts/parser-tests/test262/whitelist.txt
+++ b/scripts/parser-tests/test262/whitelist.txt
@@ -1,194 +1,16 @@
-language/expressions/class/elements/fields-duplicate-privatenames.js(default)
-language/expressions/class/elements/fields-duplicate-privatenames.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage-chained-usage.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage-chained-usage.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage-recursive.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage-recursive.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage.js(strict mode)
 language/expressions/class/elements/syntax/early-errors/grammar-private-field-on-object-destructuring.js(default)
 language/expressions/class/elements/syntax/early-errors/grammar-private-field-on-object-destructuring.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-async-gen.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-async-gen.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-async.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-async.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-gen.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-gen.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-get-field.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-get-field.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-get-get.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-get-get.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-meth-field.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-meth-field.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-meth-get.js(default)
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-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-set-field.js(strict mode)
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-language/expressions/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-set-set.js(strict mode)
-language/expressions/class/elements/syntax/early-errors/grammar-privatename-in-computed-property-missing.js(default)
-language/expressions/class/elements/syntax/early-errors/grammar-privatename-in-computed-property-missing.js(strict mode)
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-language/expressions/class/elements/syntax/early-errors/invalid-names/field-init-call-expression-bad-reference.js(strict mode)
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 language/expressions/object/method-definition/private-name-early-error-async-gen-inside-class.js(default)
 language/expressions/object/method-definition/private-name-early-error-async-gen-inside-class.js(strict mode)
+language/expressions/object/method-definition/private-name-early-error-async-gen.js(default)
+language/expressions/object/method-definition/private-name-early-error-async-gen.js(strict mode)
 language/expressions/object/method-definition/private-name-early-error-gen-inside-class.js(default)
 language/expressions/object/method-definition/private-name-early-error-gen-inside-class.js(strict mode)
+language/expressions/object/method-definition/private-name-early-error-gen.js(default)
+language/expressions/object/method-definition/private-name-early-error-gen.js(strict mode)
 language/expressions/object/method-definition/private-name-early-error-method-inside-class.js(default)
 language/expressions/object/method-definition/private-name-early-error-method-inside-class.js(strict mode)
-language/module-code/privatename-not-valid-earlyerr-module-1.js(default)
-language/module-code/privatename-not-valid-earlyerr-module-1.js(strict mode)
-language/module-code/privatename-not-valid-earlyerr-module-2.js(default)
-language/module-code/privatename-not-valid-earlyerr-module-2.js(strict mode)
-language/module-code/privatename-not-valid-earlyerr-module-3.js(default)
-language/module-code/privatename-not-valid-earlyerr-module-3.js(strict mode)
-language/module-code/privatename-not-valid-earlyerr-module-4.js(default)
-language/module-code/privatename-not-valid-earlyerr-module-4.js(strict mode)
-language/statements/class/elements/fields-duplicate-privatenames.js(default)
-language/statements/class/elements/fields-duplicate-privatenames.js(strict mode)
-language/statements/class/elements/privatename-not-valid-earlyerr-script-1.js(default)
-language/statements/class/elements/privatename-not-valid-earlyerr-script-1.js(strict mode)
-language/statements/class/elements/privatename-not-valid-earlyerr-script-2.js(default)
-language/statements/class/elements/privatename-not-valid-earlyerr-script-2.js(strict mode)
-language/statements/class/elements/privatename-not-valid-earlyerr-script-3.js(default)
-language/statements/class/elements/privatename-not-valid-earlyerr-script-3.js(strict mode)
-language/statements/class/elements/privatename-not-valid-earlyerr-script-4.js(default)
-language/statements/class/elements/privatename-not-valid-earlyerr-script-4.js(strict mode)
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-language/statements/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage-chained-usage.js(strict mode)
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-language/statements/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage.js(strict mode)
+language/expressions/object/method-definition/private-name-early-error-method.js(default)
+language/expressions/object/method-definition/private-name-early-error-method.js(strict mode)
 language/statements/class/elements/syntax/early-errors/grammar-private-field-on-object-destructuring.js(default)
 language/statements/class/elements/syntax/early-errors/grammar-private-field-on-object-destructuring.js(strict mode)
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-language/statements/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-set-field.js(default)
-language/statements/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-set-field.js(strict mode)
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-language/statements/class/elements/syntax/early-errors/grammar-privatemeth-duplicate-set-set.js(strict mode)
-language/statements/class/elements/syntax/early-errors/grammar-privatename-in-computed-property-missing.js(default)
-language/statements/class/elements/syntax/early-errors/grammar-privatename-in-computed-property-missing.js(strict mode)
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-language/statements/class/elements/syntax/early-errors/invalid-names/field-init-call-expression-bad-reference.js(strict mode)
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