diff --git a/src/wp-includes/rest-api/class-wp-rest-server.php b/src/wp-includes/rest-api/class-wp-rest-server.php
index b7451ffc18..1a94dd3fcf 100644
--- a/src/wp-includes/rest-api/class-wp-rest-server.php
+++ b/src/wp-includes/rest-api/class-wp-rest-server.php
@@ -1229,6 +1229,7 @@ class WP_REST_Server {
 		$response->add_link( 'help', 'https://developer.wordpress.org/rest-api/' );
 		$this->add_active_theme_link_to_index( $response );
 		$this->add_site_logo_to_index( $response );
+		$this->add_site_icon_to_index( $response );
 
 		/**
 		 * Filters the REST API root index data.
@@ -1275,6 +1276,7 @@ class WP_REST_Server {
 
 	/**
 	 * Exposes the site logo through the WordPress REST API.
+	 *
 	 * This is used for fetching this information when user has no rights
 	 * to update settings.
 	 *
@@ -1283,14 +1285,47 @@ class WP_REST_Server {
 	 * @param WP_REST_Response $response REST API response.
 	 */
 	protected function add_site_logo_to_index( WP_REST_Response $response ) {
-		$site_logo_id                = get_theme_mod( 'custom_logo' );
-		$response->data['site_logo'] = $site_logo_id;
-		if ( $site_logo_id ) {
+		$site_logo_id = get_theme_mod( 'custom_logo', 0 );
+
+		$this->add_image_to_index( $response, $site_logo_id, 'site_logo' );
+	}
+
+	/**
+	 * Exposes the site icon through the WordPress REST API.
+	 *
+	 * This is used for fetching this information when user has no rights
+	 * to update settings.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @param WP_REST_Response $response REST API response.
+	 */
+	protected function add_site_icon_to_index( WP_REST_Response $response ) {
+		$site_icon_id = get_option( 'site_icon', 0 );
+
+		$this->add_image_to_index( $response, $site_icon_id, 'site_icon' );
+	}
+
+	/**
+	 * Exposes an image through the WordPress REST API.
+	 * This is used for fetching this information when user has no rights
+	 * to update settings.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @param WP_REST_Response $response REST API response.
+	 * @param int              $image_id Image attachment ID.
+	 * @param string           $type     Type of Image.
+	 */
+	protected function add_image_to_index( WP_REST_Response $response, $image_id, $type ) {
+		$response->data[ $type ] = (int) $image_id;
+		if ( $image_id ) {
 			$response->add_link(
 				'https://api.w.org/featuredmedia',
-				rest_url( rest_get_route_for_post( $site_logo_id ) ),
+				rest_url( rest_get_route_for_post( $image_id ) ),
 				array(
 					'embeddable' => true,
+					'type'       => $type,
 				)
 			);
 		}
diff --git a/tests/phpunit/tests/rest-api/rest-server.php b/tests/phpunit/tests/rest-api/rest-server.php
index 57951463ae..248886a76e 100644
--- a/tests/phpunit/tests/rest-api/rest-server.php
+++ b/tests/phpunit/tests/rest-api/rest-server.php
@@ -10,6 +10,13 @@
  * @group restapi
  */
 class Tests_REST_Server extends WP_Test_REST_TestCase {
+	protected static $icon_id;
+
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
+		$filename      = DIR_TESTDATA . '/images/test-image-large.jpg';
+		self::$icon_id = $factory->attachment->create_upload_object( $filename );
+	}
+
 	public function set_up() {
 		parent::set_up();
 
@@ -1007,6 +1014,24 @@ class Tests_REST_Server extends WP_Test_REST_TestCase {
 
 		$this->assertArrayHasKey( 'help', $index->get_links() );
 		$this->assertArrayNotHasKey( 'wp:active-theme', $index->get_links() );
+
+		// Check site icon.
+		$this->assertArrayHasKey( 'site_icon', $data );
+	}
+
+	/**
+	 * @ticket 52321
+	 */
+	public function test_get_index_with_site_icon() {
+		$server = new WP_REST_Server();
+		update_option( 'site_icon', self::$icon_id );
+
+		$request = new WP_REST_Request( 'GET', '/' );
+		$index   = $server->dispatch( $request );
+		$data    = $index->get_data();
+
+		$this->assertArrayHasKey( 'site_icon', $data );
+		$this->assertEquals( self::$icon_id, $data['site_icon'] );
 	}
 
 	public function test_get_namespace_index() {
diff --git a/tests/qunit/fixtures/wp-api-generated.js b/tests/qunit/fixtures/wp-api-generated.js
index 9ec0077690..f6c0026248 100644
--- a/tests/qunit/fixtures/wp-api-generated.js
+++ b/tests/qunit/fixtures/wp-api-generated.js
@@ -10369,7 +10369,8 @@ mockedApiResponse.Schema = {
             ]
         }
     },
-    "site_logo": false
+    "site_logo": 0,
+    "site_icon": 0
 };
 
 mockedApiResponse.oembed = {