diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/__snapshots__/index.test.ts.snap b/packages/docusaurus-plugin-content-docs/src/__tests__/__snapshots__/index.test.ts.snap
index 35d26aa8a5..0d601a5d24 100644
--- a/packages/docusaurus-plugin-content-docs/src/__tests__/__snapshots__/index.test.ts.snap
+++ b/packages/docusaurus-plugin-content-docs/src/__tests__/__snapshots__/index.test.ts.snap
@@ -1491,6 +1491,7 @@ Object {
       "unversionedId": "installation",
     },
   ],
+  "isCategoryIndex": [Function],
   "item": Object {
     "dirName": ".",
     "type": "autogenerated",
diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/docs.test.ts b/packages/docusaurus-plugin-content-docs/src/__tests__/docs.test.ts
index a5cd7c5c31..f00525b88e 100644
--- a/packages/docusaurus-plugin-content-docs/src/__tests__/docs.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/__tests__/docs.test.ts
@@ -12,7 +12,7 @@ import {
   readVersionDocs,
   readDocFile,
   addDocNavigation,
-  isConventionalDocIndex,
+  isCategoryIndex,
 } from '../docs';
 import {loadSidebars} from '../sidebars';
 import {readVersionsMetadata} from '../versions';
@@ -938,108 +938,124 @@ describe('versioned site', () => {
 describe('isConventionalDocIndex', () => {
   test('supports readme', () => {
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'readme.md',
+      isCategoryIndex({
+        fileName: 'readme',
+        directories: ['doesNotMatter'],
+        extension: '.md',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'readme.mdx',
+      isCategoryIndex({
+        fileName: 'readme',
+        directories: ['doesNotMatter'],
+        extension: '.mdx',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'README.md',
+      isCategoryIndex({
+        fileName: 'README',
+        directories: ['doesNotMatter'],
+        extension: '.md',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'parent/ReAdMe',
+      isCategoryIndex({
+        fileName: 'ReAdMe',
+        directories: ['doesNotMatter'],
+        extension: '',
       }),
     ).toEqual(true);
   });
 
   test('supports index', () => {
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'index.md',
+      isCategoryIndex({
+        fileName: 'index',
+        directories: ['doesNotMatter'],
+        extension: '.md',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'index.mdx',
+      isCategoryIndex({
+        fileName: 'index',
+        directories: ['doesNotMatter'],
+        extension: '.mdx',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'INDEX.md',
+      isCategoryIndex({
+        fileName: 'INDEX',
+        directories: ['doesNotMatter'],
+        extension: '.md',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'parent/InDeX',
+      isCategoryIndex({
+        fileName: 'InDeX',
+        directories: ['doesNotMatter'],
+        extension: '',
       }),
     ).toEqual(true);
   });
 
   test('supports <categoryName>/<categoryName>.md', () => {
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'someCategory',
-        source: 'someCategory',
+      isCategoryIndex({
+        fileName: 'someCategory',
+        directories: ['someCategory', 'doesNotMatter'],
+        extension: '',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'someCategory',
-        source: 'someCategory.md',
+      isCategoryIndex({
+        fileName: 'someCategory',
+        directories: ['someCategory'],
+        extension: '.md',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'someCategory',
-        source: 'someCategory.mdx',
+      isCategoryIndex({
+        fileName: 'someCategory',
+        directories: ['someCategory'],
+        extension: '.mdx',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'some_category',
-        source: 'SOME_CATEGORY.md',
+      isCategoryIndex({
+        fileName: 'SOME_CATEGORY',
+        directories: ['some_category'],
+        extension: '.md',
       }),
     ).toEqual(true);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'some_category',
-        source: 'parent/some_category',
+      isCategoryIndex({
+        fileName: 'some_category',
+        directories: ['some_category'],
+        extension: '',
       }),
     ).toEqual(true);
   });
 
   test('reject other cases', () => {
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'someCategory',
-        source: 'some_Category',
+      isCategoryIndex({
+        fileName: 'some_Category',
+        directories: ['someCategory'],
+        extension: '',
       }),
     ).toEqual(false);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'read_me',
+      isCategoryIndex({
+        fileName: 'read_me',
+        directories: ['doesNotMatter'],
+        extension: '',
       }),
     ).toEqual(false);
     expect(
-      isConventionalDocIndex({
-        sourceDirName: 'doesNotMatter',
-        source: 'the index',
+      isCategoryIndex({
+        fileName: 'the index',
+        directories: ['doesNotMatter'],
+        extension: '',
       }),
     ).toEqual(false);
   });
diff --git a/packages/docusaurus-plugin-content-docs/src/docs.ts b/packages/docusaurus-plugin-content-docs/src/docs.ts
index 9925156250..9002479b9a 100644
--- a/packages/docusaurus-plugin-content-docs/src/docs.ts
+++ b/packages/docusaurus-plugin-content-docs/src/docs.ts
@@ -8,7 +8,7 @@
 import path from 'path';
 import fs from 'fs-extra';
 import logger from '@docusaurus/logger';
-import {keyBy, last} from 'lodash';
+import {keyBy} from 'lodash';
 import {
   aliasedSitePath,
   getEditUrl,
@@ -41,6 +41,8 @@ import {toDocNavigationLink, toNavigationLink} from './sidebars/utils';
 import type {
   MetadataOptions,
   PluginOptions,
+  CategoryIndexMatcher,
+  CategoryIndexMatcherParam,
 } from '@docusaurus/plugin-content-docs';
 
 type LastUpdateOptions = Pick<
@@ -367,31 +369,62 @@ export function getMainDocId({
   return getMainDoc().unversionedId;
 }
 
-function getLastPathSegment(str: string): string {
-  return last(str.split('/'))!;
-}
-
 // By convention, Docusaurus considers some docs are "indexes":
 // - index.md
 // - readme.md
 // - <folder>/<folder>.md
 //
+// This function is the default implementation of this convention
+//
 // Those index docs produce a different behavior
 // - Slugs do not end with a weird "/index" suffix
 // - Auto-generated sidebar categories link to them as intro
-export function isConventionalDocIndex(doc: {
-  source: DocMetadataBase['slug'];
-  sourceDirName: DocMetadataBase['sourceDirName'];
-}): boolean {
-  // "@site/docs/folder/subFolder/subSubFolder/myDoc.md" => "myDoc"
-  const docName = path.parse(doc.source).name;
+export const isCategoryIndex: CategoryIndexMatcher = ({
+  fileName,
+  directories,
+}): boolean => {
+  const eligibleDocIndexNames = [
+    'index',
+    'readme',
+    directories[0]?.toLowerCase(),
+  ];
+  return eligibleDocIndexNames.includes(fileName.toLowerCase());
+};
 
-  // "folder/subFolder/subSubFolder" => "subSubFolder"
-  const lastDirName = getLastPathSegment(doc.sourceDirName);
+export function toCategoryIndexMatcherParam({
+  source,
+  sourceDirName,
+}: Pick<
+  DocMetadataBase,
+  'source' | 'sourceDirName'
+>): CategoryIndexMatcherParam {
+  // source + sourceDirName are always posix-style
+  return {
+    fileName: path.posix.parse(source).name,
+    extension: path.posix.parse(source).ext,
+    directories: sourceDirName.split(path.posix.sep).reverse(),
+  };
+}
 
-  const eligibleDocIndexNames = ['index', 'readme', lastDirName.toLowerCase()];
-
-  return eligibleDocIndexNames.includes(docName.toLowerCase());
+/**
+ * guides/sidebar/autogenerated.md -> 'autogenerated', '.md', ['sidebar', 'guides']
+ */
+export function splitPath(str: string): {
+  /**
+   * The list of directories, from lowest level to highest.
+   * If there's no dir name, directories is ['.']
+   */
+  directories: string[];
+  /** The file name, without extension */
+  fileName: string;
+  /** The extension, with a leading dot */
+  extension: string;
+} {
+  return {
+    fileName: path.parse(str).name,
+    extension: path.parse(str).ext,
+    directories: path.dirname(str).split(path.sep).reverse(),
+  };
 }
 
 // Return both doc ids
diff --git a/packages/docusaurus-plugin-content-docs/src/plugin-content-docs.d.ts b/packages/docusaurus-plugin-content-docs/src/plugin-content-docs.d.ts
index 130de3b2c9..59f54a69c7 100644
--- a/packages/docusaurus-plugin-content-docs/src/plugin-content-docs.d.ts
+++ b/packages/docusaurus-plugin-content-docs/src/plugin-content-docs.d.ts
@@ -13,6 +13,15 @@ declare module '@docusaurus/plugin-content-docs' {
     numberPrefix?: number;
   };
 
+  export type CategoryIndexMatcherParam = {
+    fileName: string;
+    directories: string[];
+    extension: string;
+  };
+  export type CategoryIndexMatcher = (
+    param: CategoryIndexMatcherParam,
+  ) => boolean;
+
   export type EditUrlFunction = (editUrlParams: {
     version: string;
     versionDocsDirPath: string;
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
index defbe97a2c..67e7073294 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/generator.test.ts
@@ -12,6 +12,7 @@ import {
 import type {Sidebar, SidebarItemsGenerator} from '../types';
 import fs from 'fs-extra';
 import {DefaultNumberPrefixParser} from '../../numberPrefix';
+import {isCategoryIndex} from '../../docs';
 
 describe('DefaultSidebarItemsGenerator', () => {
   function testDefaultSidebarItemsGenerator(
@@ -19,6 +20,7 @@ describe('DefaultSidebarItemsGenerator', () => {
   ) {
     return DefaultSidebarItemsGenerator({
       numberPrefixParser: DefaultNumberPrefixParser,
+      isCategoryIndex,
       item: {
         type: 'autogenerated',
         dirName: '.',
@@ -146,6 +148,7 @@ describe('DefaultSidebarItemsGenerator', () => {
 
     const sidebarSlice = await DefaultSidebarItemsGenerator({
       numberPrefixParser: DefaultNumberPrefixParser,
+      isCategoryIndex,
       item: {
         type: 'autogenerated',
         dirName: '.',
@@ -157,48 +160,48 @@ describe('DefaultSidebarItemsGenerator', () => {
       docs: [
         {
           id: 'intro',
-          source: 'intro.md',
+          source: '@site/docs/intro.md',
           sourceDirName: '.',
           sidebarPosition: 1,
           frontMatter: {},
         },
         {
           id: 'tutorials-index',
-          source: 'index.md',
+          source: '@site/docs/01-Tutorials/index.md',
           sourceDirName: '01-Tutorials',
           sidebarPosition: 2,
           frontMatter: {},
         },
         {
           id: 'tutorial2',
-          source: 'tutorial2.md',
+          source: '@site/docs/01-Tutorials/tutorial2.md',
           sourceDirName: '01-Tutorials',
           sidebarPosition: 2,
           frontMatter: {},
         },
         {
           id: 'tutorial1',
-          source: 'tutorial1.md',
+          source: '@site/docs/01-Tutorials/tutorial1.md',
           sourceDirName: '01-Tutorials',
           sidebarPosition: 1,
           frontMatter: {},
         },
         {
           id: 'guides-index',
-          source: '02-Guides.md', // TODO should we allow to just use "Guides.md" to have an index?
+          source: '@site/docs/02-Guides/02-Guides.md', // TODO should we allow to just use "Guides.md" to have an index?
           sourceDirName: '02-Guides',
           frontMatter: {},
         },
         {
           id: 'guide2',
-          source: 'guide2.md',
+          source: '@site/docs/02-Guides/guide2.md',
           sourceDirName: '02-Guides',
           sidebarPosition: 2,
           frontMatter: {},
         },
         {
           id: 'guide1',
-          source: 'guide1.md',
+          source: '@site/docs/02-Guides/guide1.md',
           sourceDirName: '02-Guides',
           sidebarPosition: 1,
           frontMatter: {
@@ -207,14 +210,14 @@ describe('DefaultSidebarItemsGenerator', () => {
         },
         {
           id: 'nested-guide',
-          source: 'nested-guide.md',
+          source: '@site/docs/02-Guides/01-SubGuides/nested-guide.md',
           sourceDirName: '02-Guides/01-SubGuides',
           sidebarPosition: undefined,
           frontMatter: {},
         },
         {
           id: 'end',
-          source: 'end.md',
+          source: '@site/docs/end.md',
           sourceDirName: '.',
           sidebarPosition: 3,
           frontMatter: {},
@@ -296,6 +299,7 @@ describe('DefaultSidebarItemsGenerator', () => {
 
     const sidebarSlice = await DefaultSidebarItemsGenerator({
       numberPrefixParser: DefaultNumberPrefixParser,
+      isCategoryIndex,
       item: {
         type: 'autogenerated',
         dirName: 'subfolder/subsubfolder',
@@ -427,19 +431,19 @@ describe('DefaultSidebarItemsGenerator', () => {
       docs: [
         {
           id: 'parent/doc1',
-          source: 'index.md',
+          source: '@site/docs/Category/index.md',
           sourceDirName: 'Category',
           frontMatter: {},
         },
         {
           id: 'parent/doc2',
-          source: 'index.md',
+          source: '@site/docs/Category/index.md',
           sourceDirName: 'Category',
           frontMatter: {},
         },
         {
           id: 'parent/doc3',
-          source: 'doc3.md',
+          source: '@site/docs/Category/doc3.md',
           sourceDirName: 'Category',
           frontMatter: {},
         },
@@ -473,4 +477,116 @@ describe('DefaultSidebarItemsGenerator', () => {
       },
     ] as Sidebar);
   });
+
+  test('respects custom isCategoryIndex', async () => {
+    const sidebarSlice = await DefaultSidebarItemsGenerator({
+      numberPrefixParser: DefaultNumberPrefixParser,
+      isCategoryIndex({fileName, directories}) {
+        return (
+          fileName.replace(
+            `${DefaultNumberPrefixParser(
+              directories[0],
+            ).filename.toLowerCase()}-`,
+            '',
+          ) === 'index'
+        );
+      },
+      item: {
+        type: 'autogenerated',
+        dirName: '.',
+      },
+      version: {
+        versionName: 'current',
+        contentPath: '',
+      },
+      docs: [
+        {
+          id: 'intro',
+          source: '@site/docs/intro.md',
+          sourceDirName: '.',
+          sidebarPosition: 1,
+          frontMatter: {},
+        },
+        {
+          id: 'tutorials-index',
+          source: '@site/docs/01-Tutorials/tutorials-index.md',
+          sourceDirName: '01-Tutorials',
+          sidebarPosition: 2,
+          frontMatter: {},
+        },
+        {
+          id: 'tutorial2',
+          source: '@site/docs/01-Tutorials/tutorial2.md',
+          sourceDirName: '01-Tutorials',
+          sidebarPosition: 2,
+          frontMatter: {},
+        },
+        {
+          id: 'tutorial1',
+          source: '@site/docs/01-Tutorials/tutorial1.md',
+          sourceDirName: '01-Tutorials',
+          sidebarPosition: 1,
+          frontMatter: {},
+        },
+        {
+          id: 'not-guides-index',
+          source: '@site/docs/02-Guides/README.md',
+          sourceDirName: '02-Guides',
+          frontMatter: {},
+        },
+        {
+          id: 'guide2',
+          source: '@site/docs/02-Guides/guide2.md',
+          sourceDirName: '02-Guides',
+          sidebarPosition: 2,
+          frontMatter: {},
+        },
+        {
+          id: 'guide1',
+          source: '@site/docs/02-Guides/guide1.md',
+          sourceDirName: '02-Guides',
+          sidebarPosition: 1,
+          frontMatter: {
+            sidebar_class_name: 'foo',
+          },
+        },
+      ],
+      options: {
+        sidebarCollapsed: true,
+        sidebarCollapsible: true,
+      },
+    });
+
+    expect(sidebarSlice).toEqual([
+      {type: 'doc', id: 'intro'},
+      {
+        type: 'category',
+        label: 'Tutorials',
+        collapsed: true,
+        collapsible: true,
+        link: {
+          type: 'doc',
+          id: 'tutorials-index',
+        },
+        items: [
+          {type: 'doc', id: 'tutorial1'},
+          {type: 'doc', id: 'tutorial2'},
+        ],
+      },
+      {
+        type: 'category',
+        label: 'Guides',
+        collapsed: true,
+        collapsible: true,
+        items: [
+          {type: 'doc', id: 'guide1', className: 'foo'},
+          {type: 'doc', id: 'guide2'},
+          {
+            type: 'doc',
+            id: 'not-guides-index',
+          },
+        ],
+      },
+    ] as Sidebar);
+  });
 });
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/processor.test.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/processor.test.ts
index b7caeae4de..3341d8c399 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/processor.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/__tests__/processor.test.ts
@@ -16,6 +16,7 @@ import {DefaultSidebarItemsGenerator} from '../generator';
 import {createSlugger} from '@docusaurus/utils';
 import type {VersionMetadata} from '../../types';
 import {DefaultNumberPrefixParser} from '../../numberPrefix';
+import {isCategoryIndex} from '../../docs';
 
 describe('processSidebars', () => {
   function createStaticSidebarItemGenerator(
@@ -137,6 +138,7 @@ describe('processSidebars', () => {
         versionName: version.versionName,
       },
       numberPrefixParser: DefaultNumberPrefixParser,
+      isCategoryIndex,
       options: params.sidebarOptions,
     });
     expect(StaticSidebarItemsGenerator).toHaveBeenCalledWith({
@@ -147,6 +149,7 @@ describe('processSidebars', () => {
         versionName: version.versionName,
       },
       numberPrefixParser: DefaultNumberPrefixParser,
+      isCategoryIndex,
       options: params.sidebarOptions,
     });
     expect(StaticSidebarItemsGenerator).toHaveBeenCalledWith({
@@ -157,6 +160,7 @@ describe('processSidebars', () => {
         versionName: version.versionName,
       },
       numberPrefixParser: DefaultNumberPrefixParser,
+      isCategoryIndex,
       options: params.sidebarOptions,
     });
 
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
index acd534a993..0807112cba 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/generator.ts
@@ -25,7 +25,7 @@ import path from 'path';
 import fs from 'fs-extra';
 import Yaml from 'js-yaml';
 import {validateCategoryMetadataFile} from './validation';
-import {createDocsByIdIndex, isConventionalDocIndex} from '../docs';
+import {createDocsByIdIndex, toCategoryIndexMatcherParam} from '../docs';
 
 const BreadcrumbSeparator = '/';
 // To avoid possible name clashes with a folder of the same name as the ID
@@ -94,6 +94,7 @@ async function readCategoryMetadataFile(
 // Comment for this feature: https://github.com/facebook/docusaurus/issues/3464#issuecomment-818670449
 export const DefaultSidebarItemsGenerator: SidebarItemsGenerator = async ({
   numberPrefixParser,
+  isCategoryIndex,
   docs: allDocs,
   options,
   item: {dirName: autogenDir},
@@ -210,10 +211,13 @@ export const DefaultSidebarItemsGenerator: SidebarItemsGenerator = async ({
       }
 
       function findConventionalCategoryDocLink(): SidebarItemDoc | undefined {
-        return allItems.find(
-          (item) =>
-            item.type === 'doc' && isConventionalDocIndex(getDoc(item.id)),
-        ) as SidebarItemDoc | undefined;
+        return allItems.find((item) => {
+          if (item.type !== 'doc') {
+            return false;
+          }
+          const doc = getDoc(item.id);
+          return isCategoryIndex(toCategoryIndexMatcherParam(doc));
+        }) as SidebarItemDoc | undefined;
       }
 
       function getCategoryLinkedDocId(): string | undefined {
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/processor.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/processor.ts
index e1ec68fbc2..0ef94ba25f 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/processor.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/processor.ts
@@ -25,6 +25,7 @@ import {DefaultSidebarItemsGenerator} from './generator';
 import {mapValues, memoize, pick} from 'lodash';
 import combinePromises from 'combine-promises';
 import {normalizeItem} from './normalization';
+import {isCategoryIndex} from '../docs';
 import type {Slugger} from '@docusaurus/utils';
 import type {
   NumberPrefixParser,
@@ -95,6 +96,7 @@ async function processSidebar(
       item,
       numberPrefixParser,
       defaultSidebarItemsGenerator: DefaultSidebarItemsGenerator,
+      isCategoryIndex,
       ...getSidebarItemsGeneratorDocsAndVersion(),
       options: sidebarOptions,
     });
diff --git a/packages/docusaurus-plugin-content-docs/src/sidebars/types.ts b/packages/docusaurus-plugin-content-docs/src/sidebars/types.ts
index 8d6c61ecf3..56a4be084a 100644
--- a/packages/docusaurus-plugin-content-docs/src/sidebars/types.ts
+++ b/packages/docusaurus-plugin-content-docs/src/sidebars/types.ts
@@ -10,6 +10,7 @@ import type {DocMetadataBase, VersionMetadata} from '../types';
 import type {
   NumberPrefixParser,
   SidebarOptions,
+  CategoryIndexMatcher,
 } from '@docusaurus/plugin-content-docs';
 
 // Makes all properties visible when hovering over the type
@@ -195,6 +196,7 @@ export type SidebarItemsGeneratorArgs = {
   version: SidebarItemsGeneratorVersion;
   docs: SidebarItemsGeneratorDoc[];
   numberPrefixParser: NumberPrefixParser;
+  isCategoryIndex: CategoryIndexMatcher;
   options: SidebarOptions;
 };
 export type SidebarItemsGenerator = (
diff --git a/packages/docusaurus-plugin-content-docs/src/slug.ts b/packages/docusaurus-plugin-content-docs/src/slug.ts
index 6d84e9b176..e5168563c2 100644
--- a/packages/docusaurus-plugin-content-docs/src/slug.ts
+++ b/packages/docusaurus-plugin-content-docs/src/slug.ts
@@ -16,7 +16,7 @@ import {
   stripPathNumberPrefixes,
 } from './numberPrefix';
 import type {DocMetadataBase} from './types';
-import {isConventionalDocIndex} from './docs';
+import {isCategoryIndex, toCategoryIndexMatcherParam} from './docs';
 import type {NumberPrefixParser} from '@docusaurus/plugin-content-docs';
 
 export default function getSlug({
@@ -29,7 +29,7 @@ export default function getSlug({
 }: {
   baseID: string;
   frontMatterSlug?: string;
-  source: DocMetadataBase['slug'];
+  source: DocMetadataBase['source'];
   sourceDirName: DocMetadataBase['sourceDirName'];
   stripDirNumberPrefixes?: boolean;
   numberPrefixParser?: NumberPrefixParser;
@@ -50,7 +50,10 @@ export default function getSlug({
       return frontMatterSlug;
     } else {
       const dirNameSlug = getDirNameSlug();
-      if (!frontMatterSlug && isConventionalDocIndex({source, sourceDirName})) {
+      if (
+        !frontMatterSlug &&
+        isCategoryIndex(toCategoryIndexMatcherParam({source, sourceDirName}))
+      ) {
         return dirNameSlug;
       }
       const baseSlug = frontMatterSlug || baseID;
diff --git a/packages/docusaurus-plugin-content-docs/src/types.ts b/packages/docusaurus-plugin-content-docs/src/types.ts
index 4604ca1d65..b32575772f 100644
--- a/packages/docusaurus-plugin-content-docs/src/types.ts
+++ b/packages/docusaurus-plugin-content-docs/src/types.ts
@@ -82,8 +82,8 @@ export type DocMetadataBase = LastUpdateData & {
   version: string;
   title: string;
   description: string;
-  source: string; // @site aliased source => "@site/docs/folder/subFolder/subSubFolder/myDoc.md"
-  sourceDirName: string; // relative to the versioned docs folder (can be ".") => "folder/subFolder/subSubFolder"
+  source: string; // @site aliased posix source => "@site/docs/folder/subFolder/subSubFolder/myDoc.md"
+  sourceDirName: string; // posix path relative to the versioned docs folder (can be ".") => "folder/subFolder/subSubFolder"
   slug: string;
   permalink: string;
   sidebarPosition?: number;
diff --git a/website/_dogfooding/_docs tests/tests/category-links/custom-index-convention/intro.md b/website/_dogfooding/_docs tests/tests/category-links/custom-index-convention/intro.md
new file mode 100644
index 0000000000..dd647aa825
--- /dev/null
+++ b/website/_dogfooding/_docs tests/tests/category-links/custom-index-convention/intro.md	
@@ -0,0 +1,3 @@
+# Introduction
+
+This file is called `intro.md`. Typically, it won't be selected by the convention; however, it is in this case, because we have used a custom one.
diff --git a/website/_dogfooding/_docs tests/tests/category-links/custom-index-convention/sample-doc.md b/website/_dogfooding/_docs tests/tests/category-links/custom-index-convention/sample-doc.md
new file mode 100644
index 0000000000..15fb7937c3
--- /dev/null
+++ b/website/_dogfooding/_docs tests/tests/category-links/custom-index-convention/sample-doc.md	
@@ -0,0 +1,3 @@
+# Sample doc
+
+Lorem Ipsum
diff --git a/website/_dogfooding/dogfooding.config.js b/website/_dogfooding/dogfooding.config.js
index 0179dc3599..3d087da411 100644
--- a/website/_dogfooding/dogfooding.config.js
+++ b/website/_dogfooding/dogfooding.config.js
@@ -21,6 +21,20 @@ const dogfoodingPluginInstances = [
       // The target folder uses a _ prefix to test against an edge case regarding MDX partials: https://github.com/facebook/docusaurus/discussions/5181#discussioncomment-1018079
       path: fs.realpathSync('_dogfooding/docs-tests-symlink'),
       showLastUpdateTime: true,
+      sidebarItemsGenerator(args) {
+        return args.defaultSidebarItemsGenerator({
+          ...args,
+          isCategoryIndex({fileName, directories}) {
+            const eligibleDocIndexNames = [
+              'index',
+              'readme',
+              directories[0].toLowerCase(),
+              'intro',
+            ];
+            return eligibleDocIndexNames.includes(fileName.toLowerCase());
+          },
+        });
+      },
     }),
   ],
 
diff --git a/website/docs/api/plugins/plugin-content-docs.md b/website/docs/api/plugins/plugin-content-docs.md
index ef6b1aa9ac..1c706ef128 100644
--- a/website/docs/api/plugins/plugin-content-docs.md
+++ b/website/docs/api/plugins/plugin-content-docs.md
@@ -77,6 +77,12 @@ type PrefixParser = (filename: string) => {
   numberPrefix?: number;
 };
 
+type CategoryIndexMatcher = (doc: {
+  fileName: string;
+  directories: string[];
+  extension: string;
+}) => boolean;
+
 type SidebarGenerator = (generatorArgs: {
   item: {type: 'autogenerated'; dirName: string}; // the sidebar item with type "autogenerated"
   version: {contentPath: string; versionName: string}; // the current version
@@ -88,6 +94,7 @@ type SidebarGenerator = (generatorArgs: {
     sidebarPosition?: number | undefined;
   }>; // all the docs of that version (unfiltered)
   numberPrefixParser: PrefixParser; // numberPrefixParser configured for this plugin
+  isCategoryIndex: CategoryIndexMatcher; // the default category index matcher, that you can override
   defaultSidebarItemsGenerator: SidebarGenerator; // useful to re-use/enhance default sidebar generation logic from Docusaurus
 }) => Promise<SidebarItem[]>;
 
@@ -141,6 +148,7 @@ const config = {
     item,
     version,
     docs,
+    isCategoryIndex,
   }) {
     // Use the provided data to generate a custom sidebar slice
     return [
@@ -274,15 +282,15 @@ website/i18n/[locale]/docusaurus-plugin-content-docs
 │
 │ # translations for website/docs
 ├── current
-│   ├── api
-│   │   └── config.md
-│   └── getting-started.md
+│   ├── api
+│   │   └── config.md
+│   └── getting-started.md
 ├── current.json
 │
 │ # translations for website/versioned_docs/version-1.0.0
 ├── version-1.0.0
-│   ├── api
-│   │   └── config.md
-│   └── getting-started.md
+│   ├── api
+│   │   └── config.md
+│   └── getting-started.md
 └── version-1.0.0.json
 ```
diff --git a/website/docs/guides/docs/sidebar/autogenerated.md b/website/docs/guides/docs/sidebar/autogenerated.md
index f3ffe9b20c..4282e02c11 100644
--- a/website/docs/guides/docs/sidebar/autogenerated.md
+++ b/website/docs/guides/docs/sidebar/autogenerated.md
@@ -194,6 +194,102 @@ Naming your introductory document `README.md` makes it show up when browsing the
 
 :::
 
+<details>
+
+<summary>Customizing category index matching</summary>
+
+It is possible to opt out any of the category index conventions, or define even more conventions. You can inject your own `isCategoryIndex` matcher through the [`sidebarItemsGenerator`](#customize-the-sidebar-items-generator) callback. For example, you can also pick `intro` as another file name eligible for automatically becoming the category index.
+
+```js title="docusaurus.config.js"
+module.exports = {
+  plugins: [
+    [
+      '@docusaurus/plugin-content-docs',
+      {
+        async sidebarItemsGenerator({
+          ...args,
+          isCategoryIndex: defaultCategoryIndexMatcher, // The default matcher implementation, given below
+          defaultSidebarItemsGenerator,
+        }) {
+          return defaultSidebarItemsGenerator({
+            ...args,
+            // highlight-start
+            isCategoryIndex(doc) {
+              return (
+                // Also pick intro.md in addition to the default ones
+                doc.fileName.toLowerCase() === 'intro' ||
+                defaultCategoryIndexMatcher(doc)
+              );
+            },
+            // highlight-end
+          });
+        },
+      },
+    ],
+  ],
+};
+```
+
+Or choose to not have any category index convention.
+
+```js title="docusaurus.config.js"
+module.exports = {
+  plugins: [
+    [
+      '@docusaurus/plugin-content-docs',
+      {
+        async sidebarItemsGenerator({
+          ...args,
+          isCategoryIndex: defaultCategoryIndexMatcher, // The default matcher implementation, given below
+          defaultSidebarItemsGenerator,
+        }) {
+          return defaultSidebarItemsGenerator({
+            ...args,
+            // highlight-start
+            isCategoryIndex() {
+              // No doc will be automatically picked as category index
+              return false;
+            },
+            // highlight-end
+          });
+        },
+      },
+    ],
+  ],
+};
+```
+
+The `isCategoryIndex` matcher will be provided with three fields:
+
+- `fileName`, the file's name without extension and with casing preserved
+- `directories`, the list of directory names _from the lowest level to the highest level_, relative to the docs root directory
+- `extension`, the file's extension, with a leading dot.
+
+For example, for a doc file at `guides/sidebar/autogenerated.md`, the props the matcher receives are
+
+```js
+const props = {
+  fileName: 'autogenerated',
+  directories: ['sidebar', 'guides'],
+  extension: '.md',
+};
+```
+
+The default implementation is:
+
+```js
+function isCategoryIndex({fileName, directories}) {
+  const eligibleDocIndexNames = [
+    'index',
+    'readme',
+    directories[0].toLowerCase(),
+  ];
+  return eligibleDocIndexNames.includes(fileName.toLowerCase());
+}
+```
+
+</details>
+
 ## Autogenerated sidebar metadata {#autogenerated-sidebar-metadata}
 
 For hand-written sidebar definitions, you would provide metadata to sidebar items through `sidebars.js`; for autogenerated, Docusaurus would read them from the item's respective file. In addition, you may want to adjust the relative position of each item, because, by default, items within a sidebar slice will be generated in **alphabetical order** (using files and folders names).
@@ -317,6 +413,7 @@ module.exports = {
           item,
           version,
           docs,
+          isCategoryIndex,
         }) {
           // Example: return an hardcoded list of static sidebar items
           return [