diff --git a/docs/rules/no-undef.md b/docs/rules/no-undef.md
index 4b21f2c05d9..49a149fde77 100644
--- a/docs/rules/no-undef.md
+++ b/docs/rules/no-undef.md
@@ -4,7 +4,7 @@ This rule can help you locate potential ReferenceErrors resulting from misspelli
 
 ## Rule Details
 
-Any reference to an undeclared variable causes a warning, unless the variable is explicitly mentioned in a `/*global ...*/` comment.
+Any reference to an undeclared variable causes a warning, unless the variable is explicitly mentioned in a `/*global ...*/` comment, or specified in the [`globals` key in the configuration file](https://eslint.org/docs/user-guide/configuring#specifying-globals). A common use case for these is if you intentionally use globals that are defined elsewhere (e.g. in a script sourced from HTML).
 
 Examples of **incorrect** code for this rule: