diff --git a/wp-includes/class-wp-term-query.php b/wp-includes/class-wp-term-query.php
index f6f53f210c..9a9b902dea 100644
--- a/wp-includes/class-wp-term-query.php
+++ b/wp-includes/class-wp-term-query.php
@@ -87,6 +87,7 @@ class WP_Term_Query {
 	 * @since 4.6.0
 	 * @since 4.6.0 Introduced 'term_taxonomy_id' parameter.
 	 * @since 4.7.0 Introduced 'object_ids' parameter.
+	 * @since 4.9.0 Added 'slug__in' support for 'orderby'.
 	 *
 	 * @param string|array $query {
 	 *     Optional. Array or query string of term query parameters. Default empty.
@@ -98,7 +99,8 @@ class WP_Term_Query {
 	 *     @type string       $orderby                Field(s) to order terms by. Accepts term fields ('name',
 	 *                                                'slug', 'term_group', 'term_id', 'id', 'description', 'parent'),
 	 *                                                'count' for term taxonomy count, 'include' to match the
-	 *                                                'order' of the $include param, 'meta_value', 'meta_value_num',
+	 *                                                'order' of the $include param, 'slug__in' to match the
+	 *                                                'order' of the $slug param, 'meta_value', 'meta_value_num',
 	 *                                                the value of `$meta_key`, the array keys of `$meta_query`, or
 	 *                                                'none' to omit the ORDER BY clause. Defaults to 'name'.
 	 *     @type string       $order                  Whether to order terms in ascending or descending order.
@@ -841,6 +843,9 @@ class WP_Term_Query {
 		} elseif ( 'include' == $_orderby && ! empty( $this->query_vars['include'] ) ) {
 			$include = implode( ',', wp_parse_id_list( $this->query_vars['include'] ) );
 			$orderby = "FIELD( t.term_id, $include )";
+		} elseif ( 'slug__in' == $_orderby && ! empty( $this->query_vars['slug'] ) && is_array( $this->query_vars['slug'] ) ) {
+			$slugs = implode( "', '", array_map( 'sanitize_title_for_query', $this->query_vars['slug__in'] ) );
+			$orderby = "FIELD( t.slug, '" . $slugs . "')";
 		} elseif ( 'none' == $_orderby ) {
 			$orderby = '';
 		} elseif ( empty( $_orderby ) || 'id' == $_orderby || 'term_id' === $_orderby ) {
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
index 8d65252537..93a2b8db0d 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
@@ -874,9 +874,10 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 		// Map to proper WP_Query orderby param.
 		if ( isset( $query_args['orderby'] ) && isset( $request['orderby'] ) ) {
 			$orderby_mappings = array(
-				'id'      => 'ID',
-				'include' => 'post__in',
-				'slug'    => 'post_name',
+				'id'            => 'ID',
+				'include'       => 'post__in',
+				'slug'          => 'post_name',
+				'include_slugs' => 'post_name__in',
 			);
 
 			if ( isset( $orderby_mappings[ $request['orderby'] ] ) ) {
@@ -2109,6 +2110,7 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 				'parent',
 				'relevance',
 				'slug',
+				'include_slugs',
 				'title',
 			),
 		);
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php
index 826902a164..749a6d6870 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php
@@ -188,6 +188,16 @@ class WP_REST_Terms_Controller extends WP_REST_Controller {
 			}
 		}
 
+		if ( isset( $prepared_args['orderby'] ) && isset( $request['orderby'] ) ) {
+			$orderby_mappings = array(
+				'include_slugs' => 'slug__in',
+			);
+
+			if ( isset( $orderby_mappings[ $request['orderby'] ] ) ) {
+				$prepared_args['orderby'] = $orderby_mappings[ $request['orderby'] ];
+			}
+		}
+
 		if ( isset( $registered['offset'] ) && ! empty( $request['offset'] ) ) {
 			$prepared_args['offset'] = $request['offset'];
 		} else {
@@ -932,6 +942,7 @@ class WP_REST_Terms_Controller extends WP_REST_Controller {
 				'include',
 				'name',
 				'slug',
+				'include_slugs',
 				'term_group',
 				'description',
 				'count',
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
index 44d6367a54..c7c32a73db 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
@@ -243,6 +243,7 @@ class WP_REST_Users_Controller extends WP_REST_Controller {
 				'name'            => 'display_name',
 				'registered_date' => 'registered',
 				'slug'            => 'user_nicename',
+				'include_slugs'   => 'nicename__in',
 				'email'           => 'user_email',
 				'url'             => 'user_url',
 			);
@@ -1338,6 +1339,7 @@ class WP_REST_Users_Controller extends WP_REST_Controller {
 				'name',
 				'registered_date',
 				'slug',
+				'include_slugs',
 				'email',
 				'url',
 			),
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 6917766e26..c9783b2ef7 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-alpha-41759';
+$wp_version = '4.9-alpha-41760';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.