diff --git a/packages/angular_devkit/build_angular/BUILD.bazel b/packages/angular_devkit/build_angular/BUILD.bazel
index 2f23e6d8da75..c7840d0fd443 100644
--- a/packages/angular_devkit/build_angular/BUILD.bazel
+++ b/packages/angular_devkit/build_angular/BUILD.bazel
@@ -101,6 +101,7 @@ ts_library(
         "//packages/angular_devkit/core/node",
         "//packages/ngtools/webpack",
         "@npm//@ampproject/remapping",
+        "@npm//@angular/common",
         "@npm//@angular/compiler-cli",
         "@npm//@angular/core",
         "@npm//@angular/localize",
diff --git a/packages/angular_devkit/build_angular/src/utils/index-file/augment-index-html.ts b/packages/angular_devkit/build_angular/src/utils/index-file/augment-index-html.ts
index 79130bfff333..d02406844a2f 100644
--- a/packages/angular_devkit/build_angular/src/utils/index-file/augment-index-html.ts
+++ b/packages/angular_devkit/build_angular/src/utils/index-file/augment-index-html.ts
@@ -7,6 +7,7 @@
  */
 
 import { createHash } from 'crypto';
+import { loadEsmModule } from '../load-esm';
 import { htmlRewritingStream } from './html-rewriting-stream';
 
 export type LoadOutputFileFunctionType = (file: string) => Promise<string>;
@@ -50,9 +51,14 @@ export interface FileInfo {
  * after processing several configurations in order to build different sets of
  * bundles for differential serving.
  */
-export async function augmentIndexHtml(params: AugmentIndexHtmlOptions): Promise<string> {
+export async function augmentIndexHtml(
+  params: AugmentIndexHtmlOptions,
+): Promise<{ content: string; warnings: string[]; errors: string[] }> {
   const { loadOutputFile, files, entrypoints, sri, deployUrl = '', lang, baseHref, html } = params;
 
+  const warnings: string[] = [];
+  const errors: string[] = [];
+
   let { crossOrigin = 'none' } = params;
   if (sri && crossOrigin === 'none') {
     crossOrigin = 'anonymous';
@@ -119,6 +125,7 @@ export async function augmentIndexHtml(params: AugmentIndexHtmlOptions): Promise
     linkTags.push(`<link ${attrs.join(' ')}>`);
   }
 
+  const dir = lang ? await getLanguageDirection(lang, warnings) : undefined;
   const { rewriter, transformedContent } = await htmlRewritingStream(html);
   const baseTagExists = html.includes('<base');
 
@@ -130,6 +137,10 @@ export async function augmentIndexHtml(params: AugmentIndexHtmlOptions): Promise
           if (isString(lang)) {
             updateAttribute(tag, 'lang', lang);
           }
+
+          if (dir) {
+            updateAttribute(tag, 'dir', dir);
+          }
           break;
         case 'head':
           // Base href should be added before any link, meta tags
@@ -174,12 +185,15 @@ export async function augmentIndexHtml(params: AugmentIndexHtmlOptions): Promise
 
   const content = await transformedContent;
 
-  if (linkTags.length || scriptTags.length) {
-    // In case no body/head tags are not present (dotnet partial templates)
-    return linkTags.join('') + scriptTags.join('') + content;
-  }
-
-  return content;
+  return {
+    content:
+      linkTags.length || scriptTags.length
+        ? // In case no body/head tags are not present (dotnet partial templates)
+          linkTags.join('') + scriptTags.join('') + content
+        : content,
+    warnings,
+    errors,
+  };
 }
 
 function generateSriAttributes(content: string): string {
@@ -207,3 +221,21 @@ function updateAttribute(
 function isString(value: unknown): value is string {
   return typeof value === 'string';
 }
+
+async function getLanguageDirection(lang: string, warnings: string[]): Promise<string | undefined> {
+  try {
+    const localeData = (
+      await loadEsmModule<typeof import('@angular/common/locales/en')>(
+        `@angular/common/locales/${lang}`,
+      )
+    ).default;
+
+    const dir = localeData[localeData.length - 2];
+
+    return isString(dir) ? dir : undefined;
+  } catch {
+    warnings.push(
+      `Locale data for '${lang}' cannot be found. 'dir' attribute will not be set for this locale.`,
+    );
+  }
+}
diff --git a/packages/angular_devkit/build_angular/src/utils/index-file/augment-index-html_spec.ts b/packages/angular_devkit/build_angular/src/utils/index-file/augment-index-html_spec.ts
index 3d460817cec4..e0ff4b595bbf 100644
--- a/packages/angular_devkit/build_angular/src/utils/index-file/augment-index-html_spec.ts
+++ b/packages/angular_devkit/build_angular/src/utils/index-file/augment-index-html_spec.ts
@@ -28,7 +28,7 @@ describe('augment-index-html', () => {
     tags.stripIndents`${html}`.replace(/(>\s+)/g, '>');
 
   it('can generate index.html', async () => {
-    const source = augmentIndexHtml({
+    const { content } = await augmentIndexHtml({
       ...indexGeneratorOptions,
       files: [
         { file: 'styles.css', extension: '.css', name: 'styles' },
@@ -39,8 +39,7 @@ describe('augment-index-html', () => {
       ],
     });
 
-    const html = await source;
-    expect(html).toEqual(oneLineHtml`
+    expect(content).toEqual(oneLineHtml`
       <html>
         <head><base href="/">
           <link rel="stylesheet" href="styles.css">
@@ -55,14 +54,13 @@ describe('augment-index-html', () => {
   });
 
   it('should replace base href value', async () => {
-    const source = augmentIndexHtml({
+    const { content } = await augmentIndexHtml({
       ...indexGeneratorOptions,
       html: '<html><head><base href="/"></head><body></body></html>',
       baseHref: '/Apps/',
     });
 
-    const html = await source;
-    expect(html).toEqual(oneLineHtml`
+    expect(content).toEqual(oneLineHtml`
       <html>
         <head><base href="/Apps/">
       </head>
@@ -72,15 +70,51 @@ describe('augment-index-html', () => {
     `);
   });
 
-  it('should add lang attribute', async () => {
-    const source = augmentIndexHtml({
+  it('should add lang and dir LTR attribute for French (fr)', async () => {
+    const { content } = await augmentIndexHtml({
       ...indexGeneratorOptions,
       lang: 'fr',
     });
 
-    const html = await source;
-    expect(html).toEqual(oneLineHtml`
-        <html lang="fr">
+    expect(content).toEqual(oneLineHtml`
+        <html lang="fr" dir="ltr">
+          <head>
+            <base href="/">
+          </head>
+          <body>
+          </body>
+        </html>
+      `);
+  });
+
+  it('should add lang and dir RTL attribute for Pashto (ps)', async () => {
+    const { content } = await augmentIndexHtml({
+      ...indexGeneratorOptions,
+      lang: 'ps',
+    });
+
+    expect(content).toEqual(oneLineHtml`
+        <html lang="ps" dir="rtl">
+          <head>
+            <base href="/">
+          </head>
+          <body>
+          </body>
+        </html>
+      `);
+  });
+
+  it(`should work when lang (locale) is not provided by '@angular/common'`, async () => {
+    const { content, warnings } = await augmentIndexHtml({
+      ...indexGeneratorOptions,
+      lang: 'xx-XX',
+    });
+
+    expect(warnings).toEqual([
+      `Locale data for 'xx-XX' cannot be found. 'dir' attribute will not be set for this locale.`,
+    ]);
+    expect(content).toEqual(oneLineHtml`
+        <html lang="xx-XX">
           <head>
             <base href="/">
           </head>
@@ -91,7 +125,7 @@ describe('augment-index-html', () => {
   });
 
   it(`should add script and link tags even when body and head element doesn't exist`, async () => {
-    const source = augmentIndexHtml({
+    const { content } = await augmentIndexHtml({
       ...indexGeneratorOptions,
       html: `<app-root></app-root>`,
       files: [
@@ -103,8 +137,7 @@ describe('augment-index-html', () => {
       ],
     });
 
-    const html = await source;
-    expect(html).toEqual(oneLineHtml`
+    expect(content).toEqual(oneLineHtml`
       <link rel="stylesheet" href="styles.css">
       <script src="runtime.js" type="module"></script>
       <script src="polyfills.js" type="module"></script>