diff --git a/.changeset/eighty-forks-fry.md b/.changeset/eighty-forks-fry.md
new file mode 100644
index 0000000000..4a25dd128a
--- /dev/null
+++ b/.changeset/eighty-forks-fry.md
@@ -0,0 +1,5 @@
+---
+'@backstage/techdocs-common': patch
+---
+
+Use docs/README.md or README.md as fallback if docs/index.md is missing
diff --git a/packages/techdocs-common/src/stages/generate/helpers.test.ts b/packages/techdocs-common/src/stages/generate/helpers.test.ts
index fcf506098e..fdb164f44a 100644
--- a/packages/techdocs-common/src/stages/generate/helpers.test.ts
+++ b/packages/techdocs-common/src/stages/generate/helpers.test.ts
@@ -27,6 +27,7 @@ import {
   getGeneratorKey,
   getMkdocsYml,
   getRepoUrlFromLocationAnnotation,
+  patchIndexPreBuild,
   patchMkdocsYmlPreBuild,
   storeEtagMetadata,
   validateMkdocsYaml,
@@ -65,6 +66,8 @@ const mkdocsYmlWithComments = fs.readFileSync(
   resolvePath(__filename, '../__fixtures__/mkdocs_with_comments.yml'),
 );
 const mockLogger = getVoidLogger();
+const warn = jest.spyOn(mockLogger, 'warn');
+
 const rootDir = os.platform() === 'win32' ? 'C:\\rootDir' : '/rootDir';
 
 const scmIntegrations = ScmIntegrations.fromConfig(new ConfigReader({}));
@@ -286,6 +289,78 @@ describe('helpers', () => {
     });
   });
 
+  describe('patchIndexPreBuild', () => {
+    afterEach(() => {
+      warn.mockClear();
+    });
+    it('should have no effect if docs/index.md exists', async () => {
+      mockFs({
+        '/docs/index.md': 'index.md content',
+        '/docs/README.md': 'docs/README.md content',
+      });
+
+      await patchIndexPreBuild({ inputDir: '/', logger: mockLogger });
+
+      expect(fs.readFileSync('/docs/index.md', 'utf-8')).toEqual(
+        'index.md content',
+      );
+      expect(warn).not.toHaveBeenCalledWith();
+      mockFs.restore();
+    });
+
+    it("should use docs/README.md if docs/index.md doesn't exists", async () => {
+      mockFs({
+        '/docs/README.md': 'docs/README.md content',
+        '/README.md': 'main README.md content',
+      });
+
+      await patchIndexPreBuild({ inputDir: '/', logger: mockLogger });
+
+      expect(fs.readFileSync('/docs/index.md', 'utf-8')).toEqual(
+        'docs/README.md content',
+      );
+      expect(warn.mock.calls).toEqual([['docs/index.md not found.']]);
+      mockFs.restore();
+    });
+
+    it('should use README.md if neither docs/index.md or docs/README.md exist', async () => {
+      mockFs({
+        '/README.md': 'main README.md content',
+      });
+
+      await patchIndexPreBuild({ inputDir: '/', logger: mockLogger });
+
+      expect(fs.readFileSync('/docs/index.md', 'utf-8')).toEqual(
+        'main README.md content',
+      );
+      expect(warn.mock.calls).toEqual([
+        ['docs/index.md not found.'],
+        ['docs/README.md not found.'],
+        ['docs/readme.md not found.'],
+      ]);
+      mockFs.restore();
+    });
+
+    it('should not use any file as index.md if no one matches the requirements', async () => {
+      mockFs({});
+
+      await patchIndexPreBuild({ inputDir: '/', logger: mockLogger });
+
+      expect(() => fs.readFileSync('/docs/index.md', 'utf-8')).toThrow();
+      expect(warn.mock.calls).toEqual([
+        ['docs/index.md not found.'],
+        ['docs/README.md not found.'],
+        ['docs/readme.md not found.'],
+        ['README.md not found.'],
+        ['readme.md not found.'],
+        [
+          "Could not find any techdocs' index file. Please make sure at least one of /docs/index.md /docs/README.md /docs/readme.md /README.md /readme.md exists.",
+        ],
+      ]);
+      mockFs.restore();
+    });
+  });
+
   describe('addBuildTimestampMetadata', () => {
     beforeEach(() => {
       mockFs.restore();
@@ -406,7 +481,7 @@ describe('helpers', () => {
     it('should return true on when a valid docs_dir is present', async () => {
       await expect(
         validateMkdocsYaml(inputDir, mkdocsYmlWithValidDocDir.toString()),
-      ).resolves.toBeUndefined();
+      ).resolves.toBe('docs/');
     });
 
     it('should return false on absolute doc_dir path', async () => {
diff --git a/packages/techdocs-common/src/stages/generate/helpers.ts b/packages/techdocs-common/src/stages/generate/helpers.ts
index 94746c1aaa..f77b557076 100644
--- a/packages/techdocs-common/src/stages/generate/helpers.ts
+++ b/packages/techdocs-common/src/stages/generate/helpers.ts
@@ -176,24 +176,31 @@ export const getMkdocsYml = async (
  * @param {string} inputDir base dir to be used as a docs_dir path validity check
  * @param {string} mkdocsYmlFileString The string contents of the loaded
  *   mkdocs.yml or equivalent of a docs site
+ * @returns the parsed docs_dir or undefined
  */
 export const validateMkdocsYaml = async (
   inputDir: string,
   mkdocsYmlFileString: string,
-) => {
-  const mkdocsYml: any = yaml.load(mkdocsYmlFileString, {
+): Promise<string | undefined> => {
+  const mkdocsYml = yaml.load(mkdocsYmlFileString, {
     schema: MKDOCS_SCHEMA,
   });
 
+  if (mkdocsYml === null || typeof mkdocsYml !== 'object') {
+    return undefined;
+  }
+
+  const parsedMkdocsYml: Record<string, any> = mkdocsYml;
   if (
-    mkdocsYml.docs_dir &&
-    !isChildPath(inputDir, resolvePath(inputDir, mkdocsYml.docs_dir))
+    parsedMkdocsYml.docs_dir &&
+    !isChildPath(inputDir, resolvePath(inputDir, parsedMkdocsYml.docs_dir))
   ) {
     throw new Error(
       `docs_dir configuration value in mkdocs can't be an absolute directory or start with ../ for security reasons.
        Use relative paths instead which are resolved relative to your mkdocs.yml file location.`,
     );
   }
+  return parsedMkdocsYml.docs_dir;
 };
 
 /**
@@ -291,6 +298,52 @@ export const patchMkdocsYmlPreBuild = async (
   }
 };
 
+/**
+ * Update docs/index.md file before TechDocs generator uses it to generate docs site,
+ * falling back to docs/README.md or README.md in case a default docs/index.md
+ * is not provided.
+ */
+export const patchIndexPreBuild = async ({
+  inputDir,
+  logger,
+  docsDir = 'docs',
+}: {
+  inputDir: string;
+  logger: Logger;
+  docsDir?: string;
+}) => {
+  const docsPath = path.join(inputDir, docsDir);
+  const indexMdPath = path.join(docsPath, 'index.md');
+
+  if (await fs.pathExists(indexMdPath)) {
+    return;
+  }
+  logger.warn(`${path.join(docsDir, 'index.md')} not found.`);
+  const fallbacks = [
+    path.join(docsPath, 'README.md'),
+    path.join(docsPath, 'readme.md'),
+    path.join(inputDir, 'README.md'),
+    path.join(inputDir, 'readme.md'),
+  ];
+
+  await fs.ensureDir(docsPath);
+  for (const filePath of fallbacks) {
+    try {
+      await fs.copyFile(filePath, indexMdPath);
+      return;
+    } catch (error) {
+      logger.warn(`${path.relative(inputDir, filePath)} not found.`);
+    }
+  }
+
+  logger.warn(
+    `Could not find any techdocs' index file. Please make sure at least one of ${[
+      indexMdPath,
+      ...fallbacks,
+    ].join(' ')} exists.`,
+  );
+};
+
 /**
  * Update the techdocs_metadata.json to add a new build timestamp metadata. Create the .json file if it doesn't exist.
  *
diff --git a/packages/techdocs-common/src/stages/generate/techdocs.ts b/packages/techdocs-common/src/stages/generate/techdocs.ts
index 6b9a2817be..e87278c2d4 100644
--- a/packages/techdocs-common/src/stages/generate/techdocs.ts
+++ b/packages/techdocs-common/src/stages/generate/techdocs.ts
@@ -25,6 +25,7 @@ import {
 import {
   addBuildTimestampMetadata,
   getMkdocsYml,
+  patchIndexPreBuild,
   patchMkdocsYmlPreBuild,
   runCommand,
   storeEtagMetadata,
@@ -94,7 +95,7 @@ export class TechdocsGenerator implements GeneratorBase {
     const { path: mkdocsYmlPath, content } = await getMkdocsYml(inputDir);
 
     // validate the docs_dir first
-    await validateMkdocsYaml(inputDir, content);
+    const docsDir = await validateMkdocsYaml(inputDir, content);
 
     if (parsedLocationAnnotation) {
       await patchMkdocsYmlPreBuild(
@@ -103,6 +104,7 @@ export class TechdocsGenerator implements GeneratorBase {
         parsedLocationAnnotation,
         this.scmIntegrations,
       );
+      await patchIndexPreBuild({ inputDir, logger: childLogger, docsDir });
     }
 
     // Directories to bind on container