diff --git a/README.md b/README.md
index ecee210..72533a3 100644
--- a/README.md
+++ b/README.md
@@ -94,6 +94,7 @@ the [check-latest input](docs/advanced-usage.md#check-latest-version).
 The `go-version` input supports the following syntax:
 
 - Specific versions: `1.25`, `1.24.11`, `1.24.0-rc.1`, `1.23.0-beta.1`
+- Native Go versions: `go1.21`, `go1.21.5`, `go1.18beta2`, `go1.21rc2`. `go1.21` resolves to exactly `1.21.0`, unlike `1.21`, which matches patch releases.
 - SemVer version range syntax: `^1.25.1`, `~1.24.1`, `>=1.25.0-rc.1`, `<1.25.0`, `>=1.22.0 <1.24.0`
 - Aliases: `stable`, `oldstable`
 - Wildcards: `1.25.x`, `1.x`
diff --git a/__tests__/setup-go.test.ts b/__tests__/setup-go.test.ts
index c1946bd..ac62616 100644
--- a/__tests__/setup-go.test.ts
+++ b/__tests__/setup-go.test.ts
@@ -866,6 +866,11 @@ describe('setup-go', () => {
     expect(im.makeSemver('1.10rc1')).toBe('1.10.0-rc.1');
   });
 
+  it('preserves already-normalized prerelease versions', () => {
+    expect(im.makeSemver('1.18.0-beta.2')).toBe('1.18.0-beta.2');
+    expect(im.makeSemver('1.21.0-rc.2')).toBe('1.21.0-rc.2');
+  });
+
   it('converts dot zero versions', async () => {
     expect(im.makeSemver('1.13')).toBe('1.13.0');
   });
@@ -874,6 +879,102 @@ describe('setup-go', () => {
     expect(im.makeSemver('1.13.1')).toBe('1.13.1');
   });
 
+  it('isGoNativeVersion accepts supported Go-native version formats', () => {
+    expect(im.isGoNativeVersion('go1.21')).toBe(true);
+    expect(im.isGoNativeVersion('go1.21.5')).toBe(true);
+    expect(im.isGoNativeVersion('go1.18beta2')).toBe(true);
+    expect(im.isGoNativeVersion('go1.21rc2')).toBe(true);
+
+    expect(im.isGoNativeVersion('go1.21.x')).toBe(false);
+    expect(im.isGoNativeVersion('go^1.21')).toBe(false);
+    expect(im.isGoNativeVersion('1.21')).toBe(false);
+    expect(im.isGoNativeVersion('go1')).toBe(false);
+    expect(im.isGoNativeVersion('go1.21.5beta1')).toBe(false);
+    expect(im.isGoNativeVersion('go1.21.0rc1')).toBe(false);
+  });
+
+  it('accepts a Go-native go-version input and normalizes it', async () => {
+    os.platform = 'linux';
+    os.arch = 'x64';
+    inputs['go-version'] = 'go1.21';
+    findSpy.mockImplementation(() => path.normalize('/cache/go/1.21.0/x64'));
+
+    await main.run();
+
+    expect(logSpy).toHaveBeenCalledWith('Setup go version spec go1.21');
+    expect(findSpy).toHaveBeenCalledWith('go', '1.21.0', 'x64');
+    expect(logSpy).toHaveBeenCalledWith(
+      'Successfully set up Go version go1.21'
+    );
+  });
+
+  it('rejects a malformed Go-native go-version input', async () => {
+    os.platform = 'linux';
+    os.arch = 'x64';
+    inputs['go-version'] = 'go1.21.x';
+
+    await main.run();
+
+    expect(cnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('Invalid Go version "go1.21.x"')
+    );
+  });
+
+  it('accepts a Go-native go-version input with beta suffix and normalizes it', async () => {
+    os.platform = 'linux';
+    os.arch = 'x64';
+    inputs['go-version'] = 'go1.18beta2';
+    findSpy.mockImplementation(() =>
+      path.normalize('/cache/go/1.18.0-beta.2/x64')
+    );
+
+    await main.run();
+
+    expect(logSpy).toHaveBeenCalledWith('Setup go version spec go1.18beta2');
+    expect(findSpy).toHaveBeenCalledWith('go', '1.18.0-beta.2', 'x64');
+    expect(logSpy).toHaveBeenCalledWith(
+      'Successfully set up Go version go1.18beta2'
+    );
+  });
+
+  it('accepts a Go-native go-version input with rc suffix and normalizes it', async () => {
+    os.platform = 'linux';
+    os.arch = 'x64';
+    inputs['go-version'] = 'go1.21rc2';
+    findSpy.mockImplementation(() =>
+      path.normalize('/cache/go/1.21.0-rc.2/x64')
+    );
+
+    await main.run();
+
+    expect(logSpy).toHaveBeenCalledWith('Setup go version spec go1.21rc2');
+    expect(findSpy).toHaveBeenCalledWith('go', '1.21.0-rc.2', 'x64');
+    expect(logSpy).toHaveBeenCalledWith(
+      'Successfully set up Go version go1.21rc2'
+    );
+  });
+
+  it('downloads a normalized Go-native version on cache miss', async () => {
+    os.platform = 'linux';
+    os.arch = 'x64';
+    inputs['go-version'] = 'go1.13';
+
+    findSpy.mockImplementation(() => '');
+    dlSpy.mockImplementation(async () => '/some/temp/path');
+    extractTarSpy.mockImplementation(async () => '/some/other/temp/path');
+    cacheSpy.mockImplementation(async () =>
+      path.normalize('/cache/go/1.13.0/x64')
+    );
+
+    await main.run();
+
+    expect(logSpy).toHaveBeenCalledWith('Attempting to download 1.13.0...');
+    expect(dlSpy).toHaveBeenCalled();
+    expect(logSpy).toHaveBeenCalledWith(
+      'Successfully set up Go version go1.13'
+    );
+  });
+
   describe('check-latest flag', () => {
     it("use local version and don't check manifest if check-latest is not specified", async () => {
       os.platform = 'linux';
@@ -1297,6 +1398,43 @@ use .
   });
 
   describe('go-download-base-url', () => {
+    it('normalizes native versions but preserves custom download filenames', async () => {
+      os.platform = 'linux';
+      os.arch = 'x64';
+
+      const versionSpec = 'go1.21rc2';
+      const customBaseUrl = 'https://example.com/golang';
+      const toolName = im.customToolCacheName(customBaseUrl);
+      const toolPath = path.normalize(`/cache/${toolName}/1.21.0-rc.2/x64`);
+
+      inputs['go-version'] = versionSpec;
+      inputs['go-download-base-url'] = customBaseUrl;
+
+      getSpy.mockImplementationOnce(() => {
+        throw new Error('Not a JSON endpoint');
+      });
+      findSpy.mockImplementation(() => '');
+      dlSpy.mockImplementation(async () => '/some/temp/path');
+      extractTarSpy.mockImplementation(async () => '/some/other/temp/path');
+      execFileSpy.mockImplementation(() => 'go version go1.21rc2 linux/amd64');
+      cacheSpy.mockImplementation(async () => toolPath);
+
+      await main.run();
+
+      expect(findSpy).toHaveBeenCalledWith(toolName, '1.21.0-rc.2', 'x64');
+      expect(getSpy).toHaveBeenCalledWith(
+        `${customBaseUrl}/?mode=json&include=all`
+      );
+      expect(dlSpy).toHaveBeenCalledWith(
+        `${customBaseUrl}/go1.21rc2.linux-amd64.tar.gz`,
+        undefined,
+        undefined
+      );
+      expect(cnSpy).toHaveBeenCalledWith(
+        `::add-path::${path.join(toolPath, 'bin')}${osm.EOL}`
+      );
+    });
+
     it('downloads a version from custom base URL using version listing', async () => {
       os.platform = 'linux';
       os.arch = 'x64';
diff --git a/action.yml b/action.yml
index 79299e5..e66304c 100644
--- a/action.yml
+++ b/action.yml
@@ -3,7 +3,7 @@ description: 'Setup a Go environment and add it to the PATH'
 author: 'GitHub'
 inputs:
   go-version:
-    description: 'The Go version to download (if necessary) and use. Supports semver spec and ranges. Be sure to enclose this option in single quotation marks.'
+    description: 'The Go version to download (if necessary) and use. Supports native Go versions (e.g. go1.21.5), semver specs and ranges. Be sure to enclose this option in single quotation marks.'
   go-version-file:
     description: 'Path to the go.mod, go.work, .go-version, or .tool-versions file.'
   check-latest:
diff --git a/dist/setup/index.js b/dist/setup/index.js
index e8bba74..6bb75f0 100644
--- a/dist/setup/index.js
+++ b/dist/setup/index.js
@@ -41969,6 +41969,10 @@ async function getGo(versionSpec, checkLatest, auth, arch = external_os_default(
     let manifest;
     const osPlat = external_os_default().platform();
     const customBaseUrl = goDownloadBaseUrl?.replace(/\/+$/, '');
+    const originalVersionSpec = versionSpec;
+    if (isGoNativeVersion(versionSpec)) {
+        versionSpec = makeSemver(versionSpec);
+    }
     if (versionSpec === StableReleaseAlias.Stable ||
         versionSpec === StableReleaseAlias.OldStable) {
         if (customBaseUrl) {
@@ -42023,7 +42027,7 @@ async function getGo(versionSpec, checkLatest, auth, arch = external_os_default(
         const skipVersionListing = NO_VERSION_LISTING_BASE_URLS.some(url => customBaseUrl.toLowerCase() === url.toLowerCase());
         if (skipVersionListing) {
             core_info('Skipping version listing for known direct-download URL. Constructing download URL directly.');
-            info = getInfoFromDirectDownload(versionSpec, arch, customBaseUrl);
+            info = getInfoFromDirectDownload(originalVersionSpec, arch, customBaseUrl);
         }
         else {
             try {
@@ -42033,7 +42037,7 @@ async function getGo(versionSpec, checkLatest, auth, arch = external_os_default(
                 core_info('Version listing not available from custom URL. Constructing download URL directly.');
             }
             if (!info) {
-                info = getInfoFromDirectDownload(versionSpec, arch, customBaseUrl);
+                info = getInfoFromDirectDownload(originalVersionSpec, arch, customBaseUrl);
             }
         }
         try {
@@ -42043,10 +42047,10 @@ async function getGo(versionSpec, checkLatest, auth, arch = external_os_default(
         catch (err) {
             const downloadUrl = info?.downloadUrl || customBaseUrl;
             if (err instanceof HTTPError && err.httpStatusCode === 404) {
-                throw new Error(`The requested Go version ${versionSpec} is not available for platform ${osPlat}/${arch}. ` +
+                throw new Error(`The requested Go version ${originalVersionSpec} is not available for platform ${osPlat}/${arch}. ` +
                     `Download URL returned HTTP 404: ${downloadUrl}`, { cause: err });
             }
-            throw new Error(`Failed to download Go ${versionSpec} for platform ${osPlat}/${arch} ` +
+            throw new Error(`Failed to download Go ${originalVersionSpec} for platform ${osPlat}/${arch} ` +
                 `from ${downloadUrl}: ${err}`, { cause: err });
         }
     }
@@ -42335,6 +42339,10 @@ async function findMatch(versionSpec, arch = external_os_default().arch(), dlUrl
     }
     return result;
 }
+function isGoNativeVersion(version) {
+    const expression = /^go[1-9]\d*\.(0|[1-9]\d*)(?:\.(0|[1-9]\d*)|(?:beta|rc)[1-9]\d*)?$/;
+    return expression.test(version);
+}
 //
 // Convert the go version syntax into semver for semver matching
 // 1.13.1 => 1.13.1
@@ -42342,6 +42350,10 @@ async function findMatch(versionSpec, arch = external_os_default().arch(), dlUrl
 // 1.10beta1 => 1.10.0-beta.1, 1.10rc1 => 1.10.0-rc.1
 // 1.8.5beta1 => 1.8.5-beta.1, 1.8.5rc1 => 1.8.5-rc.1
 function makeSemver(version) {
+    const validVersion = node_modules_semver.valid(version);
+    if (validVersion) {
+        return validVersion;
+    }
     version = version.replace('go', '');
     version = version.replace('beta', '-beta.').replace('rc', '-rc.');
     const parts = version.split('-');
@@ -97835,6 +97847,13 @@ function resolveVersionInput() {
         warning('Both go-version and go-version-file inputs are specified, only go-version will be used');
     }
     if (version) {
+        const customBaseUrl = getInput('go-download-base-url') ||
+            process.env['GO_DOWNLOAD_BASE_URL'];
+        if (version.startsWith('go') &&
+            !customBaseUrl &&
+            !isGoNativeVersion(version)) {
+            throw new Error(`Invalid Go version "${version}". Go-native versions must look like go1.21, go1.21.5, go1.18beta2, or go1.21rc2. For version ranges, use SemVer syntax (e.g. ~1.21, ^1.21).`);
+        }
         return version;
     }
     if (versionFilePath) {
diff --git a/docs/advanced-usage.md b/docs/advanced-usage.md
index 0e3efa5..5cc2543 100644
--- a/docs/advanced-usage.md
+++ b/docs/advanced-usage.md
@@ -50,9 +50,13 @@ steps:
 - The preinstalled patch version is generally the latest available. When a new patch is released, it replaces the previously preinstalled version on the runner.
 - Using the most recent patch version speeds up setup because the required Go version is already installed on the runner and no download is needed.
 
+The `go-version` input also accepts native Go version strings: `go1.21.5`, `go1.18beta2`, and `go1.21rc2` normalize to `1.21.5`, `1.18.0-beta.2`, and `1.21.0-rc.2`, respectively. `go1.21` resolves to exactly `1.21.0`; use `1.21` for matching patch releases. For ranges and wildcards, use SemVer syntax such as `~1.21` or `1.21.x`, not `go1.21.x`.
+
 To try a **pre-release**:
 Download and use beta or RC Go versions as needed.
 
+The `go-version` input also accepts native Go version strings: `go1.21.5`, `go1.18beta2`, and `go1.21rc2` normalize to `1.21.5`, `1.18.0-beta.2`, and `1.21.0-rc.2`, respectively. `go1.21` resolves to exactly `1.21.0`; use `1.21` for matching patch releases. For ranges and wildcards, use SemVer syntax such as `~1.21` or `1.21.x`, not `go1.21.x`.
+
 ```yaml
 # RC version
 steps:
@@ -459,6 +463,8 @@ The `go-download-base-url` input lets you download Go from a mirror or alternati
 
 When a custom base URL is provided, the action skips the `actions/go-versions` manifest lookup and downloads directly from the specified URL.
 
+> **Note:** When constructing direct-download filenames, the original version string is preserved; native Go version normalization is used only for matching and tool cache lookups.
+
 **Using the [Microsoft build of Go](https://github.com/microsoft/go):**
 
 ```yaml
diff --git a/src/installer.ts b/src/installer.ts
index 1354d7b..a497bfd 100644
--- a/src/installer.ts
+++ b/src/installer.ts
@@ -60,6 +60,11 @@ export async function getGo(
   const osPlat: string = os.platform();
   const customBaseUrl = goDownloadBaseUrl?.replace(/\/+$/, '');
 
+  const originalVersionSpec = versionSpec;
+  if (isGoNativeVersion(versionSpec)) {
+    versionSpec = makeSemver(versionSpec);
+  }
+
   if (
     versionSpec === StableReleaseAlias.Stable ||
     versionSpec === StableReleaseAlias.OldStable
@@ -146,7 +151,11 @@ export async function getGo(
       core.info(
         'Skipping version listing for known direct-download URL. Constructing download URL directly.'
       );
-      info = getInfoFromDirectDownload(versionSpec, arch, customBaseUrl);
+      info = getInfoFromDirectDownload(
+        originalVersionSpec,
+        arch,
+        customBaseUrl
+      );
     } else {
       try {
         info = await getInfoFromDist(versionSpec, arch, customBaseUrl);
@@ -156,7 +165,11 @@ export async function getGo(
         );
       }
       if (!info) {
-        info = getInfoFromDirectDownload(versionSpec, arch, customBaseUrl);
+        info = getInfoFromDirectDownload(
+          originalVersionSpec,
+          arch,
+          customBaseUrl
+        );
       }
     }
 
@@ -167,13 +180,13 @@ export async function getGo(
       const downloadUrl = info?.downloadUrl || customBaseUrl;
       if (err instanceof tc.HTTPError && err.httpStatusCode === 404) {
         throw new Error(
-          `The requested Go version ${versionSpec} is not available for platform ${osPlat}/${arch}. ` +
+          `The requested Go version ${originalVersionSpec} is not available for platform ${osPlat}/${arch}. ` +
             `Download URL returned HTTP 404: ${downloadUrl}`,
           {cause: err}
         );
       }
       throw new Error(
-        `Failed to download Go ${versionSpec} for platform ${osPlat}/${arch} ` +
+        `Failed to download Go ${originalVersionSpec} for platform ${osPlat}/${arch} ` +
           `from ${downloadUrl}: ${err}`,
         {cause: err}
       );
@@ -610,6 +623,12 @@ export async function findMatch(
   return result;
 }
 
+export function isGoNativeVersion(version: string): boolean {
+  const expression =
+    /^go[1-9]\d*\.(0|[1-9]\d*)(?:\.(0|[1-9]\d*)|(?:beta|rc)[1-9]\d*)?$/;
+  return expression.test(version);
+}
+
 //
 // Convert the go version syntax into semver for semver matching
 // 1.13.1 => 1.13.1
@@ -617,6 +636,10 @@ export async function findMatch(
 // 1.10beta1 => 1.10.0-beta.1, 1.10rc1 => 1.10.0-rc.1
 // 1.8.5beta1 => 1.8.5-beta.1, 1.8.5rc1 => 1.8.5-rc.1
 export function makeSemver(version: string): string {
+  const validVersion = semver.valid(version);
+  if (validVersion) {
+    return validVersion;
+  }
   version = version.replace('go', '');
   version = version.replace('beta', '-beta.').replace('rc', '-rc.');
   const parts = version.split('-');
diff --git a/src/main.ts b/src/main.ts
index b1c9a49..56a2706 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -215,6 +215,18 @@ function resolveVersionInput(): string {
   }
 
   if (version) {
+    const customBaseUrl =
+      core.getInput('go-download-base-url') ||
+      process.env['GO_DOWNLOAD_BASE_URL'];
+    if (
+      version.startsWith('go') &&
+      !customBaseUrl &&
+      !installer.isGoNativeVersion(version)
+    ) {
+      throw new Error(
+        `Invalid Go version "${version}". Go-native versions must look like go1.21, go1.21.5, go1.18beta2, or go1.21rc2. For version ranges, use SemVer syntax (e.g. ~1.21, ^1.21).`
+      );
+    }
     return version;
   }