diff --git a/README.md b/README.md
index ecee210..cd669a9 100644
--- a/README.md
+++ b/README.md
@@ -94,10 +94,13 @@ 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`
 
+> **Note:** Native Go version validation and normalization apply only when no custom download base URL is configured. When `go-download-base-url` or `GO_DOWNLOAD_BASE_URL` is set, the `go-version` input is passed through unchanged.
+
 For details on Semantic Versioning, see [the semver package documentation](https://github.com/npm/node-semver).
 
 > **Note**: Due to the peculiarities of YAML parsing, it is recommended to wrap the version in single quotation marks:
diff --git a/__tests__/setup-go.test.ts b/__tests__/setup-go.test.ts
index c1946bd..5bfc1a7 100644
--- a/__tests__/setup-go.test.ts
+++ b/__tests__/setup-go.test.ts
@@ -874,6 +874,121 @@ 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 1.21.0');
+    expect(findSpy).toHaveBeenCalledWith('go', '1.21.0', 'x64');
+    expect(logSpy).toHaveBeenCalledWith(
+      'Successfully set up Go version 1.21.0'
+    );
+  });
+
+  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 1.18.0-beta.2');
+    expect(findSpy).toHaveBeenCalledWith('go', '1.18.0-beta.2', 'x64');
+    expect(logSpy).toHaveBeenCalledWith(
+      'Successfully set up Go version 1.18.0-beta.2'
+    );
+  });
+
+  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 1.21.0-rc.2');
+    expect(findSpy).toHaveBeenCalledWith('go', '1.21.0-rc.2', 'x64');
+    expect(logSpy).toHaveBeenCalledWith(
+      'Successfully set up Go version 1.21.0-rc.2'
+    );
+  });
+
+  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 1.13.0'
+    );
+  });
+
+  it('keeps go-prefixed version unchanged when a custom download URL is set', async () => {
+    os.platform = 'linux';
+    os.arch = 'x64';
+
+    const customBaseUrl = 'https://example.com/golang';
+    inputs['go-version'] = 'go1.25.1';
+    inputs['go-download-base-url'] = customBaseUrl;
+
+    const toolName = im.customToolCacheName(customBaseUrl);
+    findSpy.mockImplementation(() =>
+      path.normalize(`/cache/${toolName}/1.25.1/x64`)
+    );
+
+    await main.run();
+
+    expect(logSpy).toHaveBeenCalledWith('Setup go version spec go1.25.1');
+    expect(findSpy).toHaveBeenCalledWith(toolName, 'go1.25.1', 'x64');
+  });
+
   describe('check-latest flag', () => {
     it("use local version and don't check manifest if check-latest is not specified", async () => {
       os.platform = 'linux';
diff --git a/action.yml b/action.yml
index 79299e5..e66304c 100644
--- a/action.yml
+++ b/action.yml
@@ -3,7 +3,7 @@ description: 'Setup a Go environment and add it to the PATH'
 author: 'GitHub'
 inputs:
   go-version:
-    description: 'The Go version to download (if necessary) and use. Supports semver spec and ranges. Be sure to enclose this option in single quotation marks.'
+    description: 'The Go version to download (if necessary) and use. Supports native Go versions (e.g. go1.21.5), semver specs and ranges. Be sure to enclose this option in single quotation marks.'
   go-version-file:
     description: 'Path to the go.mod, go.work, .go-version, or .tool-versions file.'
   check-latest:
diff --git a/dist/setup/index.js b/dist/setup/index.js
index e8bba74..4ef95a4 100644
--- a/dist/setup/index.js
+++ b/dist/setup/index.js
@@ -42335,6 +42335,10 @@ async function findMatch(versionSpec, arch = external_os_default().arch(), dlUrl
     }
     return result;
 }
+function isGoNativeVersion(version) {
+    const expression = /^go[1-9]\d*\.(0|[1-9]\d*)(?:\.(0|[1-9]\d*)|(?:beta|rc)[1-9]\d*)?$/;
+    return expression.test(version);
+}
 //
 // Convert the go version syntax into semver for semver matching
 // 1.13.1 => 1.13.1
@@ -97835,6 +97839,15 @@ function resolveVersionInput() {
         warning('Both go-version and go-version-file inputs are specified, only go-version will be used');
     }
     if (version) {
+        // With a custom download URL leave the version unchanged.
+        const customBaseUrl = getInput('go-download-base-url') ||
+            process.env['GO_DOWNLOAD_BASE_URL'];
+        if (version.startsWith('go') && !customBaseUrl) {
+            if (!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).`);
+            }
+            version = makeSemver(version);
+        }
         return version;
     }
     if (versionFilePath) {
diff --git a/docs/advanced-usage.md b/docs/advanced-usage.md
index 0e3efa5..dbffded 100644
--- a/docs/advanced-usage.md
+++ b/docs/advanced-usage.md
@@ -53,6 +53,8 @@ steps:
 To try a **pre-release**:
 Download and use beta or RC Go versions as needed.
 
+When no custom download base URL is configured, 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:
diff --git a/src/installer.ts b/src/installer.ts
index 1354d7b..be05fe8 100644
--- a/src/installer.ts
+++ b/src/installer.ts
@@ -610,6 +610,12 @@ 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
diff --git a/src/main.ts b/src/main.ts
index b1c9a49..ac3d8ae 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -215,6 +215,18 @@ function resolveVersionInput(): string {
   }
 
   if (version) {
+    // With a custom download URL leave the version unchanged.
+    const customBaseUrl =
+      core.getInput('go-download-base-url') ||
+      process.env['GO_DOWNLOAD_BASE_URL'];
+    if (version.startsWith('go') && !customBaseUrl) {
+      if (!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).`
+        );
+      }
+      version = installer.makeSemver(version);
+    }
     return version;
   }