diff --git a/src/harness/client.ts b/src/harness/client.ts
index 4acfca3e0eb91..e98db818aecb5 100644
--- a/src/harness/client.ts
+++ b/src/harness/client.ts
@@ -526,6 +526,9 @@ namespace ts.server {
         private decodeSpan(span: protocol.TextSpan & { file: string }): TextSpan;
         private decodeSpan(span: protocol.TextSpan, fileName: string, lineMap?: number[]): TextSpan;
         private decodeSpan(span: protocol.TextSpan & { file: string }, fileName?: string, lineMap?: number[]): TextSpan {
+            if (span.start.line === 1 && span.start.offset === 1 && span.end.line === 1 && span.end.offset === 1) {
+                return { start: 0, length: 0 };
+            }
             fileName = fileName || span.file;
             lineMap = lineMap || this.getLineMap(fileName);
             return createTextSpanFromBounds(
diff --git a/src/harness/fourslashImpl.ts b/src/harness/fourslashImpl.ts
index 88237aea5a25d..73d83a1fb3510 100644
--- a/src/harness/fourslashImpl.ts
+++ b/src/harness/fourslashImpl.ts
@@ -688,7 +688,7 @@ namespace FourSlash {
             this.verifyGoToXWorker(toArray(endMarker), () => this.getGoToDefinition());
         }
 
-        public verifyGoToDefinition(arg0: any, endMarkerNames?: ArrayOrSingle<string>) {
+        public verifyGoToDefinition(arg0: any, endMarkerNames?: ArrayOrSingle<string> | { file: string }) {
             this.verifyGoToX(arg0, endMarkerNames, () => this.getGoToDefinitionAndBoundSpan());
         }
 
@@ -705,7 +705,7 @@ namespace FourSlash {
                 this.languageService.getTypeDefinitionAtPosition(this.activeFile.fileName, this.currentCaretPosition));
         }
 
-        private verifyGoToX(arg0: any, endMarkerNames: ArrayOrSingle<string> | undefined, getDefs: () => readonly ts.DefinitionInfo[] | ts.DefinitionInfoAndBoundSpan | undefined) {
+        private verifyGoToX(arg0: any, endMarkerNames: ArrayOrSingle<string> | { file: string } | undefined, getDefs: () => readonly ts.DefinitionInfo[] | ts.DefinitionInfoAndBoundSpan | undefined) {
             if (endMarkerNames) {
                 this.verifyGoToXPlain(arg0, endMarkerNames, getDefs);
             }
@@ -725,7 +725,7 @@ namespace FourSlash {
             }
         }
 
-        private verifyGoToXPlain(startMarkerNames: ArrayOrSingle<string>, endMarkerNames: ArrayOrSingle<string>, getDefs: () => readonly ts.DefinitionInfo[] | ts.DefinitionInfoAndBoundSpan | undefined) {
+        private verifyGoToXPlain(startMarkerNames: ArrayOrSingle<string>, endMarkerNames: ArrayOrSingle<string> | { file: string }, getDefs: () => readonly ts.DefinitionInfo[] | ts.DefinitionInfoAndBoundSpan | undefined) {
             for (const start of toArray(startMarkerNames)) {
                 this.verifyGoToXSingle(start, endMarkerNames, getDefs);
             }
@@ -737,12 +737,12 @@ namespace FourSlash {
             }
         }
 
-        private verifyGoToXSingle(startMarkerName: string, endMarkerNames: ArrayOrSingle<string>, getDefs: () => readonly ts.DefinitionInfo[] | ts.DefinitionInfoAndBoundSpan | undefined) {
+        private verifyGoToXSingle(startMarkerName: string, endMarkerNames: ArrayOrSingle<string> | { file: string }, getDefs: () => readonly ts.DefinitionInfo[] | ts.DefinitionInfoAndBoundSpan | undefined) {
             this.goToMarker(startMarkerName);
             this.verifyGoToXWorker(toArray(endMarkerNames), getDefs, startMarkerName);
         }
 
-        private verifyGoToXWorker(endMarkers: readonly string[], getDefs: () => readonly ts.DefinitionInfo[] | ts.DefinitionInfoAndBoundSpan | undefined, startMarkerName?: string) {
+        private verifyGoToXWorker(endMarkers: readonly (string | { file: string })[], getDefs: () => readonly ts.DefinitionInfo[] | ts.DefinitionInfoAndBoundSpan | undefined, startMarkerName?: string) {
             const defs = getDefs();
             let definitions: readonly ts.DefinitionInfo[];
             let testName: string;
@@ -762,21 +762,22 @@ namespace FourSlash {
                 this.raiseError(`${testName} failed - expected to find ${endMarkers.length} definitions but got ${definitions.length}`);
             }
 
-            ts.zipWith(endMarkers, definitions, (endMarker, definition, i) => {
-                const marker = this.getMarkerByName(endMarker);
-                if (ts.comparePaths(marker.fileName, definition.fileName, /*ignoreCase*/ true) !== ts.Comparison.EqualTo || marker.position !== definition.textSpan.start) {
-                    const filesToDisplay = ts.deduplicate([marker.fileName, definition.fileName], ts.equateValues);
-                    const markers = [{ text: "EXPECTED", fileName: marker.fileName, position: marker.position }, { text: "ACTUAL", fileName: definition.fileName, position: definition.textSpan.start }];
+            ts.zipWith(endMarkers, definitions, (endMarkerOrFileResult, definition, i) => {
+                const expectedFileName = typeof endMarkerOrFileResult === "string" ? this.getMarkerByName(endMarkerOrFileResult).fileName : endMarkerOrFileResult.file;
+                const expectedPosition = typeof endMarkerOrFileResult === "string" ? this.getMarkerByName(endMarkerOrFileResult).position : 0;
+                if (ts.comparePaths(expectedFileName, definition.fileName, /*ignoreCase*/ true) !== ts.Comparison.EqualTo || expectedPosition !== definition.textSpan.start) {
+                    const filesToDisplay = ts.deduplicate([expectedFileName, definition.fileName], ts.equateValues);
+                    const markers = [{ text: "EXPECTED", fileName: expectedFileName, position: expectedPosition }, { text: "ACTUAL", fileName: definition.fileName, position: definition.textSpan.start }];
                     const text = filesToDisplay.map(fileName => {
                         const markersToRender = markers.filter(m => m.fileName === fileName).sort((a, b) => b.position - a.position);
-                        let fileContent = this.getFileContent(fileName);
+                        let fileContent = this.tryGetFileContent(fileName) || "";
                         for (const marker of markersToRender) {
                             fileContent = fileContent.slice(0, marker.position) + `\x1b[1;4m/*${marker.text}*/\x1b[0;31m` + fileContent.slice(marker.position);
                         }
                         return `// @Filename: ${fileName}\n${fileContent}`;
                     }).join("\n\n");
 
-                    this.raiseError(`${testName} failed for definition ${endMarker} (${i}): expected ${marker.fileName} at ${marker.position}, got ${definition.fileName} at ${definition.textSpan.start}\n\n${text}\n`);
+                    this.raiseError(`${testName} failed for definition ${endMarkerOrFileResult} (${i}): expected ${expectedFileName} at ${expectedPosition}, got ${definition.fileName} at ${definition.textSpan.start}\n\n${text}\n`);
                 }
             });
         }
diff --git a/src/server/protocol.ts b/src/server/protocol.ts
index 776f0ed60398f..60ec24f0f6bf0 100644
--- a/src/server/protocol.ts
+++ b/src/server/protocol.ts
@@ -987,8 +987,15 @@ namespace ts.server.protocol {
     export interface FileSpanWithContext extends FileSpan, TextSpanWithContext {
     }
 
+    export interface DefinitionInfo extends FileSpanWithContext {
+        /**
+         * When true, the file may or may not exist.
+         */
+        unverified?: boolean;
+    }
+
     export interface DefinitionInfoAndBoundSpan {
-        definitions: readonly FileSpanWithContext[];
+        definitions: readonly DefinitionInfo[];
         textSpan: TextSpan;
     }
 
diff --git a/src/services/findAllReferences.ts b/src/services/findAllReferences.ts
index c4f6c8dea756a..851d2600fc7eb 100644
--- a/src/services/findAllReferences.ts
+++ b/src/services/findAllReferences.ts
@@ -624,7 +624,7 @@ namespace ts.FindAllReferences {
             }
             if (isSourceFile(node)) {
                 const resolvedRef = GoToDefinition.getReferenceAtPosition(node, position, program);
-                if (!resolvedRef) {
+                if (!resolvedRef?.file) {
                     return undefined;
                 }
                 const moduleSymbol = program.getTypeChecker().getMergedSymbol(resolvedRef.file.symbol);
@@ -656,7 +656,7 @@ namespace ts.FindAllReferences {
             if (!symbol) {
                 // String literal might be a property (and thus have a symbol), so do this here rather than in getReferencedSymbolsSpecial.
                 if (!options.implementations && isStringLiteralLike(node)) {
-                    if (isRequireCall(node.parent, /*requireStringLiteralLikeArgument*/ true) || isExternalModuleReference(node.parent) || isImportDeclaration(node.parent) || isImportCall(node.parent)) {
+                    if (isModuleSpecifierLike(node)) {
                         const fileIncludeReasons = program.getFileIncludeReasons();
                         const referencedFileName = node.getSourceFile().resolvedModules?.get(node.text)?.resolvedFileName;
                         const referencedFile = referencedFileName ? program.getSourceFile(referencedFileName) : undefined;
diff --git a/src/services/goToDefinition.ts b/src/services/goToDefinition.ts
index 532fbbe9ba120..b77b8ed0a4ceb 100644
--- a/src/services/goToDefinition.ts
+++ b/src/services/goToDefinition.ts
@@ -2,8 +2,10 @@
 namespace ts.GoToDefinition {
     export function getDefinitionAtPosition(program: Program, sourceFile: SourceFile, position: number): readonly DefinitionInfo[] | undefined {
         const resolvedRef = getReferenceAtPosition(sourceFile, position, program);
-        if (resolvedRef) {
-            return [getDefinitionInfoForFileReference(resolvedRef.reference.fileName, resolvedRef.file.fileName)];
+        const fileReferenceDefinition = resolvedRef && [getDefinitionInfoForFileReference(resolvedRef.reference.fileName, resolvedRef.fileName, resolvedRef.unverified)] || emptyArray;
+        if (resolvedRef?.file) {
+            // If `file` is missing, do a symbol-based lookup as well
+            return fileReferenceDefinition;
         }
 
         const node = getTouchingPropertyName(sourceFile, position);
@@ -25,7 +27,7 @@ namespace ts.GoToDefinition {
         // Could not find a symbol e.g. node is string or number keyword,
         // or the symbol was an internal symbol and does not have a declaration e.g. undefined symbol
         if (!symbol) {
-            return getDefinitionInfoForIndexSignatures(node, typeChecker);
+            return concatenate(fileReferenceDefinition, getDefinitionInfoForIndexSignatures(node, typeChecker));
         }
 
         const calledDeclaration = tryGetSignatureDeclaration(typeChecker, node);
@@ -76,7 +78,7 @@ namespace ts.GoToDefinition {
             });
         }
 
-        return getDefinitionFromObjectLiteralElement(typeChecker, node) || getDefinitionFromSymbol(typeChecker, symbol, node);
+        return concatenate(fileReferenceDefinition, getDefinitionFromObjectLiteralElement(typeChecker, node) || getDefinitionFromSymbol(typeChecker, symbol, node));
     }
 
     /**
@@ -111,24 +113,42 @@ namespace ts.GoToDefinition {
         }
     }
 
-    export function getReferenceAtPosition(sourceFile: SourceFile, position: number, program: Program): { reference: FileReference, file: SourceFile } | undefined {
+    export function getReferenceAtPosition(sourceFile: SourceFile, position: number, program: Program): { reference: FileReference, fileName: string, unverified: boolean, file?: SourceFile } | undefined {
         const referencePath = findReferenceInPosition(sourceFile.referencedFiles, position);
         if (referencePath) {
             const file = program.getSourceFileFromReference(sourceFile, referencePath);
-            return file && { reference: referencePath, file };
+            return file && { reference: referencePath, fileName: file.fileName, file, unverified: false };
         }
 
         const typeReferenceDirective = findReferenceInPosition(sourceFile.typeReferenceDirectives, position);
         if (typeReferenceDirective) {
             const reference = program.getResolvedTypeReferenceDirectives().get(typeReferenceDirective.fileName);
             const file = reference && program.getSourceFile(reference.resolvedFileName!); // TODO:GH#18217
-            return file && { reference: typeReferenceDirective, file };
+            return file && { reference: typeReferenceDirective, fileName: file.fileName, file, unverified: false };
         }
 
         const libReferenceDirective = findReferenceInPosition(sourceFile.libReferenceDirectives, position);
         if (libReferenceDirective) {
             const file = program.getLibFileFromReference(libReferenceDirective);
-            return file && { reference: libReferenceDirective, file };
+            return file && { reference: libReferenceDirective, fileName: file.fileName, file, unverified: false };
+        }
+
+        if (sourceFile.resolvedModules?.size) {
+            const node = getTokenAtPosition(sourceFile, position);
+            if (isModuleSpecifierLike(node) && isExternalModuleNameRelative(node.text) && sourceFile.resolvedModules.has(node.text)) {
+                const verifiedFileName = sourceFile.resolvedModules.get(node.text)?.resolvedFileName;
+                const fileName = verifiedFileName || resolvePath(getDirectoryPath(sourceFile.fileName), node.text);
+                return {
+                    file: program.getSourceFile(fileName),
+                    fileName,
+                    reference: {
+                        pos: node.getStart(),
+                        end: node.getEnd(),
+                        fileName: node.text
+                    },
+                    unverified: !!verifiedFileName,
+                };
+            }
         }
 
         return undefined;
@@ -318,7 +338,7 @@ namespace ts.GoToDefinition {
         return find(refs, ref => textRangeContainsPositionInclusive(ref, pos));
     }
 
-    function getDefinitionInfoForFileReference(name: string, targetFileName: string): DefinitionInfo {
+    function getDefinitionInfoForFileReference(name: string, targetFileName: string, unverified: boolean): DefinitionInfo {
         return {
             fileName: targetFileName,
             textSpan: createTextSpanFromBounds(0, 0),
@@ -326,6 +346,7 @@ namespace ts.GoToDefinition {
             name,
             containerName: undefined!,
             containerKind: undefined!, // TODO: GH#18217
+            unverified,
         };
     }
 
diff --git a/src/services/services.ts b/src/services/services.ts
index 884e890dccb20..2d482fe5ae9e6 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -2492,6 +2492,17 @@ namespace ts {
             return refactor.getEditsForRefactor(getRefactorContext(file, positionOrRange, preferences, formatOptions), refactorName, actionName);
         }
 
+        function toLineColumnOffset(fileName: string, position: number): LineAndCharacter {
+            // Go to Definition supports returning a zero-length span at position 0 for
+            // non-existent files. We need to special-case the conversion of position 0
+            // to avoid a crash trying to get the text for that file, since this function
+            // otherwise assumes that 'fileName' is the name of a file that exists.
+            if (position === 0) {
+                return { line: 0, character: 0 };
+            }
+            return sourceMapper.toLineColumnOffset(fileName, position);
+        }
+
         function prepareCallHierarchy(fileName: string, position: number): CallHierarchyItem | CallHierarchyItem[] | undefined {
             synchronizeHostData();
             const declarations = CallHierarchy.resolveCallHierarchyDeclaration(program, getTouchingPropertyName(getValidSourceFile(fileName), position));
@@ -2567,7 +2578,7 @@ namespace ts {
             getAutoImportProvider,
             getApplicableRefactors,
             getEditsForRefactor,
-            toLineColumnOffset: sourceMapper.toLineColumnOffset,
+            toLineColumnOffset,
             getSourceMapper: () => sourceMapper,
             clearSourceMapperCache: () => sourceMapper.clearCache(),
             prepareCallHierarchy,
diff --git a/src/services/types.ts b/src/services/types.ts
index c09d0d7d59da3..9542ad56600fc 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -991,6 +991,7 @@ namespace ts {
         name: string;
         containerKind: ScriptElementKind;
         containerName: string;
+        unverified?: boolean;
         /* @internal */ isLocal?: boolean;
     }
 
diff --git a/src/services/utilities.ts b/src/services/utilities.ts
index d57f267ea977c..74315895927ed 100644
--- a/src/services/utilities.ts
+++ b/src/services/utilities.ts
@@ -1906,6 +1906,14 @@ namespace ts {
         });
     }
 
+    export function isModuleSpecifierLike(node: Node): node is StringLiteralLike {
+        return isStringLiteralLike(node) && (
+            isExternalModuleReference(node.parent) ||
+            isImportDeclaration(node.parent) ||
+            isRequireCall(node.parent, /*requireStringLiteralLikeArgument*/ false) && node.parent.arguments[0] === node ||
+            isImportCall(node.parent) && node.parent.arguments[0] === node);
+    }
+
     export type ObjectBindingElementWithoutPropertyName = BindingElement & { name: Identifier };
 
     export function isObjectBindingElementWithoutPropertyName(bindingElement: Node): bindingElement is ObjectBindingElementWithoutPropertyName {
diff --git a/src/testRunner/unittests/tsserver/partialSemanticServer.ts b/src/testRunner/unittests/tsserver/partialSemanticServer.ts
index 5ef5cb6ccecc4..d7af24e3167bd 100644
--- a/src/testRunner/unittests/tsserver/partialSemanticServer.ts
+++ b/src/testRunner/unittests/tsserver/partialSemanticServer.ts
@@ -1,5 +1,5 @@
 namespace ts.projectSystem {
-    describe("unittests:: tsserver:: Semantic operations on PartialSemantic server", () => {
+    describe("unittests:: tsserver:: Semantic operations on partialSemanticServer", () => {
         function setup() {
             const file1: File = {
                 path: `${tscWatch.projectRoot}/a.ts`,
@@ -204,5 +204,20 @@ function fooB() { }`
             assert.isUndefined(project.getPackageJsonAutoImportProvider());
             assert.deepEqual(project.getPackageJsonsForAutoImport(), emptyArray);
         });
+
+        it("should support go-to-definition on module specifiers", () => {
+            const { session, file1, file2 } = setup();
+            openFilesForSession([file1], session);
+            const response = session.executeCommandSeq<protocol.DefinitionAndBoundSpanRequest>({
+                command: protocol.CommandTypes.DefinitionAndBoundSpan,
+                arguments: protocolFileLocationFromSubstring(file1, `"./b"`)
+            }).response as protocol.DefinitionInfoAndBoundSpan;
+            assert.isDefined(response);
+            assert.deepEqual(response.definitions, [{
+                file: file2.path,
+                start: { line: 1, offset: 1 },
+                end: { line: 1, offset: 1 }
+            }]);
+        });
     });
 }
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index 157fab06969ba..48420cb2e3d90 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -5965,6 +5965,7 @@ declare namespace ts {
         name: string;
         containerKind: ScriptElementKind;
         containerName: string;
+        unverified?: boolean;
     }
     interface DefinitionInfoAndBoundSpan {
         definitions?: readonly DefinitionInfo[];
@@ -7286,8 +7287,14 @@ declare namespace ts.server.protocol {
     }
     interface FileSpanWithContext extends FileSpan, TextSpanWithContext {
     }
+    interface DefinitionInfo extends FileSpanWithContext {
+        /**
+         * When true, the file may or may not exist.
+         */
+        unverified?: boolean;
+    }
     interface DefinitionInfoAndBoundSpan {
-        definitions: readonly FileSpanWithContext[];
+        definitions: readonly DefinitionInfo[];
         textSpan: TextSpan;
     }
     /**
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index 25e9f24c6224d..6847f968ab894 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -5965,6 +5965,7 @@ declare namespace ts {
         name: string;
         containerKind: ScriptElementKind;
         containerName: string;
+        unverified?: boolean;
     }
     interface DefinitionInfoAndBoundSpan {
         definitions?: readonly DefinitionInfo[];
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index bf81a295f023f..845c0674a9830 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -286,6 +286,7 @@ declare namespace FourSlashInterface {
          * `verify.goToDefinition(["a", "aa"], "b");` verifies that markers "a" and "aa" have the same definition "b".
          * `verify.goToDefinition("a", ["b", "bb"]);` verifies that "a" has multiple definitions available.
          */
+        goToDefinition(startMarkerNames: ArrayOrSingle<string>, fileResult: { file: string }): void;
         goToDefinition(startMarkerNames: ArrayOrSingle<string>, endMarkerNames: ArrayOrSingle<string>): void;
         goToDefinition(startMarkerNames: ArrayOrSingle<string>, endMarkerNames: ArrayOrSingle<string>, range: Range): void;
         /** Performs `goToDefinition` for each pair. */
diff --git a/tests/cases/fourslash/goToDefinitionCSSPatternAmbientModule.ts b/tests/cases/fourslash/goToDefinitionCSSPatternAmbientModule.ts
new file mode 100644
index 0000000000000..9d595e81eb444
--- /dev/null
+++ b/tests/cases/fourslash/goToDefinitionCSSPatternAmbientModule.ts
@@ -0,0 +1,17 @@
+/// <reference path="fourslash.ts" />
+
+// @esModuleInterop: true
+
+// @Filename: index.css
+//// /*2a*/html { font-size: 16px; }
+
+// @Filename: types.ts
+//// declare module /*2b*/"*.css" {
+////   const styles: any;
+////   export = styles;
+//// }
+
+// @Filename: index.ts
+//// import styles from [|/*1*/"./index.css"|];
+
+verify.goToDefinition("1", ["2a", "2b"]);
diff --git a/tests/cases/fourslash/goToDefinitionScriptImport.ts b/tests/cases/fourslash/goToDefinitionScriptImport.ts
new file mode 100644
index 0000000000000..d576f5454ad30
--- /dev/null
+++ b/tests/cases/fourslash/goToDefinitionScriptImport.ts
@@ -0,0 +1,20 @@
+/// <reference path="fourslash.ts" />
+
+// @filename: scriptThing.ts
+//// /*1d*/console.log("woooo side effects")
+
+// @filename: stylez.css
+//// /*2d*/div {
+////   color: magenta;
+//// }
+
+// @filename: moduleThing.ts
+
+// not a module, but we should let you jump to it.
+//// import [|/*1*/"./scriptThing"|];
+
+// not JS/TS, but if we can, you should be able to jump to it.
+//// import [|/*2*/"./stylez.css"|];
+
+verify.goToDefinition("1", "1d");
+verify.goToDefinition("2", "2d");
diff --git a/tests/cases/fourslash/server/goToDefinitionScriptImportServer.ts b/tests/cases/fourslash/server/goToDefinitionScriptImportServer.ts
new file mode 100644
index 0000000000000..82e1e6ef5cea4
--- /dev/null
+++ b/tests/cases/fourslash/server/goToDefinitionScriptImportServer.ts
@@ -0,0 +1,24 @@
+/// <reference path="../fourslash.ts" />
+
+// @filename: /scriptThing.ts
+//// /*1d*/console.log("woooo side effects")
+
+// @filename: /stylez.css
+//// /*2d*/div {
+////   color: magenta;
+//// }
+
+// @filename: /moduleThing.ts
+
+// not a module, but we should let you jump to it.
+//// import [|/*1*/"./scriptThing"|];
+
+// not JS/TS, but if we can, you should be able to jump to it.
+//// import [|/*2*/"./stylez.css"|];
+
+// does not exist, but should return a response to it anyway so an editor can create it.
+//// import [|/*3*/"./foo.txt"|];
+
+verify.goToDefinition("1", "1d");
+verify.goToDefinition("2", "2d");
+verify.goToDefinition("3", { file: "/foo.txt" });