diff --git src/wp-includes/rest-api/class-wp-rest-server.php src/wp-includes/rest-api/class-wp-rest-server.php
index c69cb4834c..d06974682a 100644
--- src/wp-includes/rest-api/class-wp-rest-server.php
+++ src/wp-includes/rest-api/class-wp-rest-server.php
@@ -1017,15 +1017,16 @@ class WP_REST_Server {
 	public function get_index( $request ) {
 		// General site data.
 		$available = array(
-			'name'            => get_option( 'blogname' ),
-			'description'     => get_option( 'blogdescription' ),
-			'url'             => get_option( 'siteurl' ),
-			'home'            => home_url(),
-			'gmt_offset'      => get_option( 'gmt_offset' ),
-			'timezone_string' => get_option( 'timezone_string' ),
-			'namespaces'      => array_keys( $this->namespaces ),
-			'authentication'  => array(),
-			'routes'          => $this->get_data_for_routes( $this->get_routes(), $request['context'] ),
+			'name'                => get_option( 'blogname' ),
+			'description'         => get_option( 'blogdescription' ),
+			'url'                 => get_option( 'siteurl' ),
+			'home'                => home_url(),
+			'gmt_offset'          => get_option( 'gmt_offset' ),
+			'timezone_string'     => get_option( 'timezone_string' ),
+			'permalink_structure' => get_option( 'permalink_structure' ),
+			'namespaces'          => array_keys( $this->namespaces ),
+			'authentication'      => array(),
+			'routes'              => $this->get_data_for_routes( $this->get_routes(), $request['context'] ),
 		);
 
 		$response = new WP_REST_Response( $available );
diff --git tests/phpunit/tests/rest-api/rest-server.php tests/phpunit/tests/rest-api/rest-server.php
index cb75f4e726..37b96fdd33 100644
--- tests/phpunit/tests/rest-api/rest-server.php
+++ tests/phpunit/tests/rest-api/rest-server.php
@@ -665,6 +665,7 @@ class Tests_REST_Server extends WP_Test_REST_TestCase {
 		$this->assertArrayHasKey( 'home', $data );
 		$this->assertArrayHasKey( 'gmt_offset', $data );
 		$this->assertArrayHasKey( 'timezone_string', $data );
+		$this->assertArrayHasKey( 'permalink_structure', $data );
 		$this->assertArrayHasKey( 'namespaces', $data );
 		$this->assertArrayHasKey( 'authentication', $data );
 		$this->assertArrayHasKey( 'routes', $data );
diff --git tests/qunit/fixtures/wp-api-generated.js tests/qunit/fixtures/wp-api-generated.js
index 8c9684c9de..d0882f3249 100644
--- tests/qunit/fixtures/wp-api-generated.js
+++ tests/qunit/fixtures/wp-api-generated.js
@@ -12,6 +12,7 @@ mockedApiResponse.Schema = {
     "home": "http://example.org",
     "gmt_offset": "0",
     "timezone_string": "",
+    "permalink_structure": false,
     "namespaces": [
         "oembed/1.0",
         "wp/v2"