Index: src/wp-includes/rest-api/endpoints/class-wp-rest-post-types-controller.php
===================================================================
--- src/wp-includes/rest-api/endpoints/class-wp-rest-post-types-controller.php	(revision 39069)
+++ src/wp-includes/rest-api/endpoints/class-wp-rest-post-types-controller.php	(working copy)
@@ -153,6 +153,7 @@
 			'labels'       => $post_type->labels,
 			'name'         => $post_type->label,
 			'slug'         => $post_type->name,
+			'rest_base'    => $post_type->rest_base,
 		);
 		$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
 		$data    = $this->add_additional_fields_to_object( $data, $request );
@@ -236,6 +237,12 @@
 					'context'      => array( 'view', 'edit', 'embed' ),
 					'readonly'     => true,
 				),
+				'rest_base'            => array(
+					'description'  => __( 'REST base route for the resource.' ),
+					'type'         => 'array',
+					'context'      => array( 'view', 'edit', 'embed' ),
+					'readonly'     => true,
+				),
 			),
 		);
 		return $this->add_additional_fields_schema( $schema );
Index: src/wp-includes/rest-api/endpoints/class-wp-rest-taxonomies-controller.php
===================================================================
--- src/wp-includes/rest-api/endpoints/class-wp-rest-taxonomies-controller.php	(revision 39069)
+++ src/wp-includes/rest-api/endpoints/class-wp-rest-taxonomies-controller.php	(working copy)
@@ -187,6 +187,7 @@
 			'types'        => $taxonomy->object_type,
 			'show_cloud'   => $taxonomy->show_tagcloud,
 			'hierarchical' => $taxonomy->hierarchical,
+			'rest_base'    => $taxonomy->rest_base,
 		);
 
 		$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
@@ -282,6 +283,12 @@
 					'context'      => array( 'view', 'edit' ),
 					'readonly'     => true,
 				),
+				'rest_base'            => array(
+					'description'  => __( 'REST base route for the resource.' ),
+					'type'         => 'array',
+					'context'      => array( 'view', 'edit', 'embed' ),
+					'readonly'     => true,
+				),
 			),
 		);
 		return $this->add_additional_fields_schema( $schema );
Index: tests/phpunit/tests/rest-api/rest-post-types-controller.php
===================================================================
--- tests/phpunit/tests/rest-api/rest-post-types-controller.php	(revision 39069)
+++ tests/phpunit/tests/rest-api/rest-post-types-controller.php	(working copy)
@@ -109,7 +109,7 @@
 		$response = $this->server->dispatch( $request );
 		$data = $response->get_data();
 		$properties = $data['schema']['properties'];
-		$this->assertEquals( 6, count( $properties ) );
+		$this->assertEquals( 7, count( $properties ) );
 		$this->assertArrayHasKey( 'capabilities', $properties );
 		$this->assertArrayHasKey( 'description', $properties );
 		$this->assertArrayHasKey( 'hierarchical', $properties );
@@ -116,6 +116,7 @@
 		$this->assertArrayHasKey( 'labels', $properties );
 		$this->assertArrayHasKey( 'name', $properties );
 		$this->assertArrayHasKey( 'slug', $properties );
+		$this->assertArrayHasKey( 'rest_base', $properties );
 	}
 
 	public function test_get_additional_field_registration() {
@@ -159,6 +160,7 @@
 		$this->assertEquals( $post_type_obj->name, $data['slug'] );
 		$this->assertEquals( $post_type_obj->description, $data['description'] );
 		$this->assertEquals( $post_type_obj->hierarchical, $data['hierarchical'] );
+		$this->assertEquals( $post_type_obj->rest_base, $data['rest_base'] );
 
 		$links = test_rest_expand_compact_links( $links );
 		$this->assertEquals( rest_url( 'wp/v2/types' ), $links['collection'][0]['href'] );
Index: tests/phpunit/tests/rest-api/rest-taxonomies-controller.php
===================================================================
--- tests/phpunit/tests/rest-api/rest-taxonomies-controller.php	(revision 39069)
+++ tests/phpunit/tests/rest-api/rest-taxonomies-controller.php	(working copy)
@@ -45,6 +45,7 @@
 		$this->assertEquals( 'Tags', $data['post_tag']['name'] );
 		$this->assertEquals( 'post_tag', $data['post_tag']['slug'] );
 		$this->assertEquals( false, $data['post_tag']['hierarchical'] );
+		$this->assertEquals( 'tags', $data['post_tag']['rest_base'] );
 	}
 
 	public function test_get_items_invalid_permission_for_context() {
@@ -134,7 +135,7 @@
 		$response = $this->server->dispatch( $request );
 		$data = $response->get_data();
 		$properties = $data['schema']['properties'];
-		$this->assertEquals( 8, count( $properties ) );
+		$this->assertEquals( 9, count( $properties ) );
 		$this->assertArrayHasKey( 'capabilities', $properties );
 		$this->assertArrayHasKey( 'description', $properties );
 		$this->assertArrayHasKey( 'hierarchical', $properties );
@@ -143,6 +144,7 @@
 		$this->assertArrayHasKey( 'slug', $properties );
 		$this->assertArrayHasKey( 'show_cloud', $properties );
 		$this->assertArrayHasKey( 'types', $properties );
+		$this->assertArrayHasKey( 'rest_base', $properties );
 	}
 
 	public function tearDown() {
@@ -168,6 +170,7 @@
 		$this->assertEquals( $tax_obj->name, $data['slug'] );
 		$this->assertEquals( $tax_obj->description, $data['description'] );
 		$this->assertEquals( $tax_obj->hierarchical, $data['hierarchical'] );
+		$this->assertEquals( $tax_obj->rest_base, $data['rest_base'] );
 		$this->assertEquals( rest_url( 'wp/v2/taxonomies' ), $links['collection'][0]['href'] );
 		$this->assertArrayHasKey( 'https://api.w.org/items', $links );
 		if ( 'edit' === $context ) {