diff --git a/packages/docusaurus-plugin-content-blog/src/__tests__/options.test.ts b/packages/docusaurus-plugin-content-blog/src/__tests__/options.test.ts
index 92eae01ae5..bb0f53c5f3 100644
--- a/packages/docusaurus-plugin-content-blog/src/__tests__/options.test.ts
+++ b/packages/docusaurus-plugin-content-blog/src/__tests__/options.test.ts
@@ -40,7 +40,7 @@ describe('validateOptions', () => {
       ...defaultOptions,
       feedOptions: {type: 'rss' as const, title: 'myTitle'},
       path: 'not_blog',
-      routeBasePath: 'myBlog',
+      routeBasePath: '/myBlog',
       postsPerPage: 5,
       include: ['api/*', 'docs/*'],
     };
@@ -53,7 +53,7 @@ describe('validateOptions', () => {
   it('accepts valid user options', () => {
     const userOptions: Options = {
       ...defaultOptions,
-      routeBasePath: 'myBlog',
+      routeBasePath: '/myBlog',
       beforeDefaultRemarkPlugins: [],
       beforeDefaultRehypePlugins: [markdownPluginsFunctionStub],
       remarkPlugins: [[markdownPluginsFunctionStub, {option1: '42'}]],
diff --git a/packages/docusaurus-plugin-content-blog/src/options.ts b/packages/docusaurus-plugin-content-blog/src/options.ts
index 99c4067a9a..804169f733 100644
--- a/packages/docusaurus-plugin-content-blog/src/options.ts
+++ b/packages/docusaurus-plugin-content-blog/src/options.ts
@@ -10,6 +10,7 @@ import {
   RemarkPluginsSchema,
   RehypePluginsSchema,
   AdmonitionsSchema,
+  RouteBasePathSchema,
   URISchema,
 } from '@docusaurus/utils-validation';
 import {GlobExcludeDefault} from '@docusaurus/utils';
@@ -56,10 +57,7 @@ const PluginOptionSchema = Joi.object<PluginOptions>({
   archiveBasePath: Joi.string()
     .default(DEFAULT_OPTIONS.archiveBasePath)
     .allow(null),
-  routeBasePath: Joi.string()
-    // '' not allowed, see https://github.com/facebook/docusaurus/issues/3374
-    // .allow('')
-    .default(DEFAULT_OPTIONS.routeBasePath),
+  routeBasePath: RouteBasePathSchema.default(DEFAULT_OPTIONS.routeBasePath),
   tagsBasePath: Joi.string().default(DEFAULT_OPTIONS.tagsBasePath),
   include: Joi.array().items(Joi.string()).default(DEFAULT_OPTIONS.include),
   exclude: Joi.array().items(Joi.string()).default(DEFAULT_OPTIONS.exclude),
diff --git a/packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts b/packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts
index 47535f746c..260eaccb22 100644
--- a/packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts
+++ b/packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts
@@ -42,7 +42,7 @@ describe('normalizeDocsPluginOptions', () => {
   it('accepts correctly defined user options', () => {
     const userOptions: Options = {
       path: 'my-docs', // Path to data on filesystem, relative to site dir.
-      routeBasePath: 'my-docs', // URL Route.
+      routeBasePath: '/my-docs', // URL Route.
       tagsBasePath: 'tags', // URL Tags Route.
       include: ['**/*.{md,mdx}'], // Extensions to include.
       exclude: GlobExcludeDefault,
diff --git a/packages/docusaurus-plugin-content-docs/src/options.ts b/packages/docusaurus-plugin-content-docs/src/options.ts
index 01d97d7684..a7c2e1d1e1 100644
--- a/packages/docusaurus-plugin-content-docs/src/options.ts
+++ b/packages/docusaurus-plugin-content-docs/src/options.ts
@@ -11,6 +11,7 @@ import {
   RemarkPluginsSchema,
   RehypePluginsSchema,
   AdmonitionsSchema,
+  RouteBasePathSchema,
   URISchema,
 } from '@docusaurus/utils-validation';
 import {GlobExcludeDefault} from '@docusaurus/utils';
@@ -73,10 +74,7 @@ const OptionsSchema = Joi.object<PluginOptions>({
   editUrl: Joi.alternatives().try(URISchema, Joi.function()),
   editCurrentVersion: Joi.boolean().default(DEFAULT_OPTIONS.editCurrentVersion),
   editLocalizedFiles: Joi.boolean().default(DEFAULT_OPTIONS.editLocalizedFiles),
-  routeBasePath: Joi.string()
-    // '' not allowed, see https://github.com/facebook/docusaurus/issues/3374
-    // .allow('') ""
-    .default(DEFAULT_OPTIONS.routeBasePath),
+  routeBasePath: RouteBasePathSchema.default(DEFAULT_OPTIONS.routeBasePath),
   tagsBasePath: Joi.string().default(DEFAULT_OPTIONS.tagsBasePath),
   // @ts-expect-error: deprecated
   homePageId: Joi.any().forbidden().messages({
diff --git a/packages/docusaurus-plugin-content-pages/src/__tests__/options.test.ts b/packages/docusaurus-plugin-content-pages/src/__tests__/options.test.ts
index d92d691e7d..4112452f82 100644
--- a/packages/docusaurus-plugin-content-pages/src/__tests__/options.test.ts
+++ b/packages/docusaurus-plugin-content-pages/src/__tests__/options.test.ts
@@ -33,7 +33,7 @@ describe('normalizePagesPluginOptions', () => {
   it('accepts correctly defined user options', () => {
     const userOptions = {
       path: 'src/my-pages',
-      routeBasePath: 'my-pages',
+      routeBasePath: '/my-pages',
       include: ['**/*.{js,jsx,ts,tsx}'],
       exclude: ['**/$*/'],
     };
@@ -51,4 +51,15 @@ describe('normalizePagesPluginOptions', () => {
       });
     }).toThrowErrorMatchingInlineSnapshot(`""path" must be a string"`);
   });
+
+  it('empty routeBasePath replace default path("/")', () => {
+    expect(
+      testValidate({
+        routeBasePath: '',
+      }),
+    ).toEqual({
+      ...defaultOptions,
+      routeBasePath: '/',
+    });
+  });
 });
diff --git a/packages/docusaurus-plugin-content-pages/src/options.ts b/packages/docusaurus-plugin-content-pages/src/options.ts
index cce458f71d..014f07f119 100644
--- a/packages/docusaurus-plugin-content-pages/src/options.ts
+++ b/packages/docusaurus-plugin-content-pages/src/options.ts
@@ -10,6 +10,7 @@ import {
   RemarkPluginsSchema,
   RehypePluginsSchema,
   AdmonitionsSchema,
+  RouteBasePathSchema,
 } from '@docusaurus/utils-validation';
 import {GlobExcludeDefault} from '@docusaurus/utils';
 import type {OptionValidationContext} from '@docusaurus/types';
@@ -30,7 +31,7 @@ export const DEFAULT_OPTIONS: PluginOptions = {
 
 const PluginOptionSchema = Joi.object<PluginOptions>({
   path: Joi.string().default(DEFAULT_OPTIONS.path),
-  routeBasePath: Joi.string().default(DEFAULT_OPTIONS.routeBasePath),
+  routeBasePath: RouteBasePathSchema.default(DEFAULT_OPTIONS.routeBasePath),
   include: Joi.array().items(Joi.string()).default(DEFAULT_OPTIONS.include),
   exclude: Joi.array().items(Joi.string()).default(DEFAULT_OPTIONS.exclude),
   mdxPageComponent: Joi.string().default(DEFAULT_OPTIONS.mdxPageComponent),
diff --git a/packages/docusaurus-utils-validation/src/__tests__/__snapshots__/validationSchemas.test.ts.snap b/packages/docusaurus-utils-validation/src/__tests__/__snapshots__/validationSchemas.test.ts.snap
index 4488ab4bdb..c0d9d3dd2a 100644
--- a/packages/docusaurus-utils-validation/src/__tests__/__snapshots__/validationSchemas.test.ts.snap
+++ b/packages/docusaurus-utils-validation/src/__tests__/__snapshots__/validationSchemas.test.ts.snap
@@ -130,4 +130,12 @@ exports[`validation schemas remarkPluginsSchema: for value=false 1`] = `""value"
 
 exports[`validation schemas remarkPluginsSchema: for value=null 1`] = `""value" must be an array"`;
 
+exports[`validation schemas routeBasePathSchema: for value=[] 1`] = `""value" must be a string"`;
+
+exports[`validation schemas routeBasePathSchema: for value={} 1`] = `""value" must be a string"`;
+
+exports[`validation schemas routeBasePathSchema: for value=3 1`] = `""value" must be a string"`;
+
+exports[`validation schemas routeBasePathSchema: for value=null 1`] = `""value" must be a string"`;
+
 exports[`validation schemas uRISchema: for value="spaces are invalid in a URL" 1`] = `""value" does not look like a valid url (value='')"`;
diff --git a/packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts b/packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts
index 7c8d3e42a1..7028560736 100644
--- a/packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts
+++ b/packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts
@@ -14,6 +14,7 @@ import {
   PluginIdSchema,
   URISchema,
   PathnameSchema,
+  RouteBasePathSchema,
   ContentVisibilitySchema,
 } from '../validationSchemas';
 
@@ -24,8 +25,9 @@ function createTestHelpers({
   schema: Joi.Schema;
   defaultValue?: unknown;
 }) {
-  function testOK(value: unknown) {
-    expect(Joi.attempt(value, schema)).toEqual(value ?? defaultValue);
+  function testOK(value: unknown, options?: {normalizedValue?: unknown}) {
+    const expectedValue = options?.normalizedValue ?? value ?? defaultValue;
+    expect(Joi.attempt(value, schema)).toEqual(expectedValue);
   }
 
   function testFail(value: unknown) {
@@ -168,6 +170,29 @@ describe('validation schemas', () => {
     testFail('https://github.com/foo');
   });
 
+  it('routeBasePathSchema', () => {
+    const {testFail, testOK} = createTestHelpers({
+      schema: RouteBasePathSchema,
+      defaultValue: undefined,
+    });
+
+    testOK('', {normalizedValue: '/'});
+    testOK('/');
+    testOK('/foo', {normalizedValue: '/foo'});
+    testOK('foo', {normalizedValue: '/foo'});
+    testOK('blog', {normalizedValue: '/blog'});
+    testOK('blog/', {normalizedValue: '/blog/'});
+    testOK('prefix/blog', {normalizedValue: '/prefix/blog'});
+    testOK('prefix/blog/', {normalizedValue: '/prefix/blog/'});
+    testOK('/prefix/blog', {normalizedValue: '/prefix/blog'});
+    testOK(undefined);
+
+    testFail(3);
+    testFail([]);
+    testFail(null);
+    testFail({});
+  });
+
   it('contentVisibilitySchema', () => {
     const {testFail, testOK} = createTestHelpers({
       schema: ContentVisibilitySchema,
diff --git a/packages/docusaurus-utils-validation/src/index.ts b/packages/docusaurus-utils-validation/src/index.ts
index 8d3fd6566c..8c1dfb5ae0 100644
--- a/packages/docusaurus-utils-validation/src/index.ts
+++ b/packages/docusaurus-utils-validation/src/index.ts
@@ -20,6 +20,7 @@ export {
   RemarkPluginsSchema,
   RehypePluginsSchema,
   AdmonitionsSchema,
+  RouteBasePathSchema,
   URISchema,
   PathnameSchema,
   FrontMatterTagsSchema,
diff --git a/packages/docusaurus-utils-validation/src/validationSchemas.ts b/packages/docusaurus-utils-validation/src/validationSchemas.ts
index f5e29cf82e..0044855aee 100644
--- a/packages/docusaurus-utils-validation/src/validationSchemas.ts
+++ b/packages/docusaurus-utils-validation/src/validationSchemas.ts
@@ -5,7 +5,12 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {isValidPathname, DEFAULT_PLUGIN_ID, type Tag} from '@docusaurus/utils';
+import {
+  isValidPathname,
+  DEFAULT_PLUGIN_ID,
+  type Tag,
+  addLeadingSlash,
+} from '@docusaurus/utils';
 import Joi from './Joi';
 import {JoiFrontMatter} from './JoiFrontMatter';
 
@@ -96,6 +101,26 @@ export const PathnameSchema = Joi.string()
     '{{#label}} is not a valid pathname. Pathname should start with slash and not contain any domain or query string.',
   );
 
+// Normalized schema for url path segments: baseUrl + routeBasePath...
+// Note we only add a leading slash
+// we don't always want to enforce a trailing slash on urls such as /docs
+//
+// Examples:
+// '' => '/'
+// 'docs' => '/docs'
+// '/docs' => '/docs'
+// 'docs/' => '/docs'
+// 'prefix/docs' => '/prefix/docs'
+// TODO tighter validation: not all strings are valid path segments
+export const RouteBasePathSchema = Joi
+  // Weird Joi trick needed, otherwise value '' is not normalized...
+  .alternatives()
+  .try(Joi.string().required().allow(''))
+  .custom((value: string) =>
+    // /!\ do not add trailing slash here
+    addLeadingSlash(value),
+  );
+
 const FrontMatterTagSchema = JoiFrontMatter.alternatives()
   .try(
     JoiFrontMatter.string().required(),
diff --git a/packages/docusaurus/src/server/__tests__/configValidation.test.ts b/packages/docusaurus/src/server/__tests__/configValidation.test.ts
index 81ed54f70e..e6e0bcd225 100644
--- a/packages/docusaurus/src/server/__tests__/configValidation.test.ts
+++ b/packages/docusaurus/src/server/__tests__/configValidation.test.ts
@@ -134,6 +134,11 @@ describe('normalizeConfig', () => {
   });
 
   it('normalizes various base URLs', () => {
+    expect(
+      normalizeConfig({
+        baseUrl: '',
+      }).baseUrl,
+    ).toBe('/');
     expect(
       normalizeConfig({
         baseUrl: 'noSlash',
diff --git a/packages/docusaurus/src/server/configValidation.ts b/packages/docusaurus/src/server/configValidation.ts
index 09246c3e1e..092a634677 100644
--- a/packages/docusaurus/src/server/configValidation.ts
+++ b/packages/docusaurus/src/server/configValidation.ts
@@ -180,7 +180,10 @@ const SiteUrlSchema = Joi.string()
 
 // TODO move to @docusaurus/utils-validation
 export const ConfigSchema = Joi.object<DocusaurusConfig>({
-  baseUrl: Joi.string()
+  baseUrl: Joi
+    // Weird Joi trick needed, otherwise value '' is not normalized...
+    .alternatives()
+    .try(Joi.string().required().allow(''))
     .required()
     .custom((value: string) => addLeadingSlash(addTrailingSlash(value))),
   baseUrlIssueBanner: Joi.boolean().default(DEFAULT_CONFIG.baseUrlIssueBanner),