diff --git a/docs/docs/configuration/mcp-config/oauth.md b/docs/docs/configuration/mcp-config/oauth.md
index 4c9164cc..4c4c7be1 100644
--- a/docs/docs/configuration/mcp-config/oauth.md
+++ b/docs/docs/configuration/mcp-config/oauth.md
@@ -66,11 +66,22 @@ The MCP transport type to use for the server.
 
 ### `SITE_NAME`
 
-The target Tableau site for OAuth.
+The target Tableau site for OAuth. The user must sign in to this site unless
+[`OAUTH_LOCK_SITE`](#oauth_lock_site) is `false`.
 
-- When [`AUTH`](#auth) is `oauth`, leaving this empty means any site will be supported, determined
-  by the site the user signed into when connecting to the MCP server.
+<hr />
+
+### `OAUTH_LOCK_SITE`
+
+Whether to require the user to sign in to the site specified in [`SITE_NAME`](#site_name) when using
+OAuth.
 
+- Default: `true`
+- When `true`, the user must sign in to the site specified in [`SITE_NAME`](#site_name) (or the
+  Default site if empty).
+  - If the user already has an active Tableau session in their browser for a different site, an
+    error will be returned.
+- When `false`, the user can sign in to any site they can access.
 <hr />
 
 ### `OAUTH_REDIRECT_URI`
diff --git a/docs/src/css/custom.css b/docs/src/css/custom.css
index ed57ee55..9f25610e 100644
--- a/docs/src/css/custom.css
+++ b/docs/src/css/custom.css
@@ -3,3 +3,8 @@
  * bundles Infima by default. Infima is a CSS framework designed to
  * work well for content-centric websites.
  */
+
+table td,
+table th {
+  vertical-align: top;
+}
diff --git a/package-lock.json b/package-lock.json
index 69636455..2f161798 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@tableau/mcp-server",
-  "version": "1.13.10",
+  "version": "1.14.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@tableau/mcp-server",
-      "version": "1.13.10",
+      "version": "1.14.0",
       "license": "Apache-2.0",
       "dependencies": {
         "@modelcontextprotocol/sdk": "^1.12.1",
diff --git a/package.json b/package.json
index b42d45bf..96e5ecff 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@tableau/mcp-server",
   "description": "An MCP server for Tableau, providing a suite of tools that will make it easier for developers to build AI applications that integrate with Tableau.",
-  "version": "1.13.10",
+  "version": "1.14.0",
   "repository": {
     "type": "git",
     "url": "git+https://github.com/tableau/tableau-mcp.git"
diff --git a/src/config.test.ts b/src/config.test.ts
index 91286bb4..9d407feb 100644
--- a/src/config.test.ts
+++ b/src/config.test.ts
@@ -60,6 +60,7 @@ describe('Config', () => {
       DANGEROUSLY_DISABLE_OAUTH: undefined,
       OAUTH_ISSUER: undefined,
       OAUTH_REDIRECT_URI: undefined,
+      OAUTH_LOCK_SITE: undefined,
       OAUTH_JWE_PRIVATE_KEY: undefined,
       OAUTH_JWE_PRIVATE_KEY_PATH: undefined,
       OAUTH_JWE_PRIVATE_KEY_PASSPHRASE: undefined,
@@ -1084,6 +1085,7 @@ describe('Config', () => {
       clientIdSecretPairs: null,
       issuer: defaultOAuthEnvVars.OAUTH_ISSUER,
       redirectUri: `${defaultOAuthEnvVars.OAUTH_ISSUER}/Callback`,
+      lockSite: true,
       jwePrivateKey: '',
       jwePrivateKeyPath: defaultOAuthEnvVars.OAUTH_JWE_PRIVATE_KEY_PATH,
       jwePrivateKeyPassphrase: undefined,
@@ -1103,6 +1105,7 @@ describe('Config', () => {
         issuer: '',
         clientIdSecretPairs: null,
         redirectUri: '',
+        lockSite: true,
         jwePrivateKey: '',
         jwePrivateKeyPath: '',
         jwePrivateKeyPassphrase: undefined,
@@ -1160,6 +1163,20 @@ describe('Config', () => {
       });
     });
 
+    it('should set lockSite to the specified value when OAUTH_LOCK_SITE is set', () => {
+      process.env = {
+        ...process.env,
+        ...defaultOAuthEnvVars,
+        OAUTH_LOCK_SITE: 'false',
+      };
+
+      const config = new Config();
+      expect(config.oauth).toEqual({
+        ...defaultOAuthConfig,
+        lockSite: false,
+      });
+    });
+
     it('should set jwePrivateKey to the specified value when OAUTH_JWE_PRIVATE_KEY is set', () => {
       process.env = {
         ...process.env,
diff --git a/src/config.ts b/src/config.ts
index 677b27a9..8e0093ac 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -68,6 +68,7 @@ export class Config {
     enabled: boolean;
     issuer: string;
     redirectUri: string;
+    lockSite: boolean;
     jwePrivateKey: string;
     jwePrivateKeyPath: string;
     jwePrivateKeyPassphrase: string | undefined;
@@ -122,6 +123,7 @@ export class Config {
       TABLEAU_SERVER_VERSION_CHECK_INTERVAL_IN_HOURS: tableauServerVersionCheckIntervalInHours,
       DANGEROUSLY_DISABLE_OAUTH: disableOauth,
       OAUTH_ISSUER: oauthIssuer,
+      OAUTH_LOCK_SITE: oauthLockSite,
       OAUTH_JWE_PRIVATE_KEY: oauthJwePrivateKey,
       OAUTH_JWE_PRIVATE_KEY_PATH: oauthJwePrivateKeyPath,
       OAUTH_JWE_PRIVATE_KEY_PASSPHRASE: oauthJwePrivateKeyPassphrase,
@@ -193,6 +195,7 @@ export class Config {
       enabled: disableOauthOverride ? false : !!oauthIssuer,
       issuer: oauthIssuer ?? '',
       redirectUri: redirectUri || (oauthIssuer ? `${oauthIssuer}/Callback` : ''),
+      lockSite: oauthLockSite !== 'false', // Site locking is enabled by default
       jwePrivateKey: oauthJwePrivateKey ?? '',
       jwePrivateKeyPath: oauthJwePrivateKeyPath ?? '',
       jwePrivateKeyPassphrase: oauthJwePrivateKeyPassphrase || undefined,
diff --git a/src/scripts/createClaudeMcpBundleManifest.ts b/src/scripts/createClaudeMcpBundleManifest.ts
index 70d8cb62..69c363fc 100644
--- a/src/scripts/createClaudeMcpBundleManifest.ts
+++ b/src/scripts/createClaudeMcpBundleManifest.ts
@@ -396,6 +396,14 @@ const envVars = {
     required: false,
     sensitive: false,
   },
+  OAUTH_LOCK_SITE: {
+    includeInUserConfig: false,
+    type: 'boolean',
+    title: 'OAuth Lock Site',
+    description: 'Whether to lock the site when using OAuth.',
+    required: false,
+    sensitive: false,
+  },
   OAUTH_CLIENT_ID_SECRET_PAIRS: {
     includeInUserConfig: false,
     type: 'string',
diff --git a/src/server/oauth/authorize.ts b/src/server/oauth/authorize.ts
index 99d64b5f..d6abfef8 100644
--- a/src/server/oauth/authorize.ts
+++ b/src/server/oauth/authorize.ts
@@ -133,10 +133,50 @@ export function authorize(
     oauthUrl.searchParams.set('device_name', getDeviceName(redirect_uri, state ?? ''));
     oauthUrl.searchParams.set('client_type', 'tableau-mcp');
 
-    res.redirect(oauthUrl.toString());
+    if (config.oauth.lockSite) {
+      // The "redirected" parameter is used by Tableau's OAuth controller to determine whether the user will be shown the site picker.
+      // When provided, the user will not be shown the site picker.
+      oauthUrl.searchParams.set('redirected', 'true');
+    }
+
+    const redirectUrl = await getOAuthRedirectUrl(oauthUrl, { lockSite: config.oauth.lockSite });
+    res.redirect(redirectUrl.toString());
   });
 }
 
+async function getOAuthRedirectUrl(
+  initialOAuthUrl: URL,
+  { lockSite }: { lockSite: boolean },
+): Promise<URL> {
+  if (lockSite) {
+    // When the site is locked, Tableau does the right thing and never shows the site picker,
+    // regardless of whether the user already has an active Tableau session in their browser.
+    return initialOAuthUrl;
+  }
+
+  // When the site is not locked, Tableau does the right thing and shows the site picker, but only on Cloud.
+  // On Server, if the user does not have an active Tableau session in their browser,
+  // Tableau does not show the site picker.
+  // We can force it to by changing the path from #/signin to #/site.
+
+  try {
+    const response = await fetch(initialOAuthUrl, { redirect: 'manual' });
+    if (response.status === 302) {
+      // The response is a redirect to the Tableau OAuth login page.
+      // Force it to ultimately show the site picker by changing the path from #/signin to #/site.
+      const location = response.headers.get('location');
+      if (location?.startsWith('#/signin') || location?.startsWith('/#/signin')) {
+        const locationUrl = new URL(location.replace('#/signin', '#/site'), initialOAuthUrl.origin);
+        return locationUrl;
+      }
+    }
+  } catch {
+    return initialOAuthUrl;
+  }
+
+  return initialOAuthUrl;
+}
+
 // https://client.dev/servers
 async function getClientFromMetadataDoc(
   clientMetadataUrl: URL,
diff --git a/src/server/oauth/callback.ts b/src/server/oauth/callback.ts
index 13c42752..b37d3e4b 100644
--- a/src/server/oauth/callback.ts
+++ b/src/server/oauth/callback.ts
@@ -39,10 +39,19 @@ export function callback(
     const { error, code, state } = result.data;
 
     if (error) {
-      res.status(400).json({
-        error: 'access_denied',
-        error_description: 'User denied authorization',
-      });
+      if (error === 'invalid_request') {
+        res.status(400).json({
+          error: 'invalid_request',
+          error_description:
+            'Invalid request. Did you sign in to the wrong site? From your browser, please sign out of your site and reconnect your agent to Tableau MCP.',
+        });
+      } else {
+        res.status(400).json({
+          error: 'access_denied',
+          error_description: 'User denied authorization',
+        });
+      }
+
       return;
     }
 
@@ -114,6 +123,24 @@ export function callback(
         return;
       }
 
+      if (
+        config.oauth.lockSite &&
+        sessionResult.value.site.name !== config.siteName &&
+        !(sessionResult.value.site.name === 'Default' && !config.siteName)
+      ) {
+        const sentences = [
+          `User signed in to site: ${sessionResult.value.site.name || 'Default'}.`,
+          `Expected site: ${config.siteName || 'Default'}.`,
+          `Please reconnect your client and choose the [${config.siteName || 'Default'}] site in the site picker if prompted.`,
+        ];
+
+        res.status(400).json({
+          error: 'invalid_request',
+          error_description: sentences.join(' '),
+        });
+        return;
+      }
+
       // Generate authorization code
       const authorizationCode = randomBytes(32).toString('hex');
       authorizationCodes.set(authorizationCode, {
diff --git a/tests/oauth/authorizationCodeCallback.test.ts b/tests/oauth/authorizationCodeCallback.test.ts
index 469605dd..aa33f996 100644
--- a/tests/oauth/authorizationCodeCallback.test.ts
+++ b/tests/oauth/authorizationCodeCallback.test.ts
@@ -27,6 +27,7 @@ describe('authorization code callback', () => {
   });
 
   afterEach(async () => {
+    vi.unstubAllEnvs();
     await new Promise<void>((resolve) => {
       if (_server) {
         _server.close(() => {
@@ -49,6 +50,22 @@ describe('authorization code callback', () => {
     return { app };
   }
 
+  it('should reject if the request is invalid', async () => {
+    const { app } = await startServer();
+
+    const response = await request(app).get('/Callback').query({
+      error: 'invalid_request',
+    });
+
+    expect(response.status).toBe(400);
+    expect(response.headers['content-type']).toBe('application/json; charset=utf-8');
+    expect(response.body).toEqual({
+      error: 'invalid_request',
+      error_description:
+        'Invalid request. Did you sign in to the wrong site? From your browser, please sign out of your site and reconnect your agent to Tableau MCP.',
+    });
+  });
+
   it('should reject if user denies authorization', async () => {
     const { app } = await startServer();
 
@@ -152,7 +169,95 @@ describe('authorization code callback', () => {
     });
   });
 
-  it('should issue an authorization code when the Tableau access token is successfully retrieved', async () => {
+  it('should reject if the user signs in to a different site other than the locked, expected site', async () => {
+    vi.stubEnv('SITE_NAME', 'other-site');
+
+    const { app } = await startServer();
+
+    const authzResponse = await request(app).get('/oauth/authorize').query({
+      client_id: 'test-client-id',
+      redirect_uri: 'http://localhost:3000',
+      response_type: 'code',
+      code_challenge: 'test-code-challenge',
+      code_challenge_method: 'S256',
+      state: 'test-state',
+    });
+
+    const authzLocation = new URL(authzResponse.headers['location']);
+    const [authKey, tableauState] = authzLocation.searchParams.get('state')?.split(':') ?? [];
+
+    mocks.mockGetTokenResult.mockResolvedValue({
+      accessToken: 'test-access-token',
+      refreshToken: 'test-refresh-token',
+      expiresInSeconds: 3600,
+      originHost: '10ax.online.tableau.com',
+    });
+
+    const response = await request(app)
+      .get('/Callback')
+      .query({
+        code: 'test-code',
+        state: `${authKey}:${tableauState}`,
+      });
+
+    expect(response.status).toBe(400);
+    expect(response.headers['content-type']).toBe('application/json; charset=utf-8');
+    expect(response.body).toEqual({
+      error: 'invalid_request',
+      error_description:
+        'User signed in to site: mcp-test. Expected site: other-site. Please reconnect your client and choose the [other-site] site in the site picker if prompted.',
+    });
+  });
+
+  it('should issue an authorization code when the Tableau access token is successfully retrieved when site locking is disabled', async () => {
+    vi.stubEnv('SITE_NAME', 'other-site');
+    vi.stubEnv('OAUTH_LOCK_SITE', 'false');
+
+    const { app } = await startServer();
+
+    const authzResponse = await request(app).get('/oauth/authorize').query({
+      client_id: 'test-client-id',
+      redirect_uri: 'http://localhost:3000',
+      response_type: 'code',
+      code_challenge: 'test-code-challenge',
+      code_challenge_method: 'S256',
+      state: 'test-state',
+    });
+
+    const authzLocation = new URL(authzResponse.headers['location']);
+    const searchParams = new URLSearchParams(
+      authzLocation.hash.substring(authzLocation.hash.indexOf('?')),
+    );
+
+    const externalRedirectUrl = new URL(
+      searchParams.get('externalRedirect') ?? '',
+      authzLocation.origin,
+    );
+
+    const [authKey, tableauState] = externalRedirectUrl.searchParams.get('state')?.split(':') ?? [];
+
+    mocks.mockGetTokenResult.mockResolvedValue({
+      accessToken: 'test-access-token',
+      refreshToken: 'test-refresh-token',
+      expiresInSeconds: 3600,
+      originHost: '10ax.online.tableau.com',
+    });
+
+    const response = await request(app)
+      .get('/Callback')
+      .query({
+        code: 'test-code',
+        state: `${authKey}:${tableauState}`,
+      });
+
+    expect(response.status).toBe(302);
+    const location = new URL(response.headers['location']);
+    expect(location.origin).toBe('http://localhost:3000');
+    expect(location.searchParams.get('code')).not.toBeNull();
+    expect(location.searchParams.get('state')).toBe('test-state');
+  });
+
+  it('should issue an authorization code when the Tableau access token is successfully retrieved when site locking is enabled', async () => {
     const { app } = await startServer();
 
     const authzResponse = await request(app).get('/oauth/authorize').query({
diff --git a/tests/oauth/testSetup.ts b/tests/oauth/testSetup.ts
index 80a6f937..28d0e29c 100644
--- a/tests/oauth/testSetup.ts
+++ b/tests/oauth/testSetup.ts
@@ -13,7 +13,7 @@ vi.mock('../../src/sdks/tableau/restApi.js', async (importOriginal) => ({
         Ok({
           site: {
             id: 'site_id',
-            name: 'test-site',
+            name: 'mcp-test',
           },
           user: {
             id: 'user_id',
diff --git a/types/process-env.d.ts b/types/process-env.d.ts
index eefc11c6..4852b5c5 100644
--- a/types/process-env.d.ts
+++ b/types/process-env.d.ts
@@ -45,6 +45,7 @@ export interface ProcessEnvEx {
   OAUTH_JWE_PRIVATE_KEY_PASSPHRASE: string | undefined;
   OAUTH_CIMD_DNS_SERVERS: string | undefined;
   OAUTH_REDIRECT_URI: string | undefined;
+  OAUTH_LOCK_SITE: string | undefined;
   OAUTH_CLIENT_ID_SECRET_PAIRS: string | undefined;
   OAUTH_AUTHORIZATION_CODE_TIMEOUT_MS: string | undefined;
   OAUTH_ACCESS_TOKEN_TIMEOUT_MS: string | undefined;