diff --git a/wp-includes/class-wp-post-type.php b/wp-includes/class-wp-post-type.php
index faf7a0d496..0099515050 100644
--- a/wp-includes/class-wp-post-type.php
+++ b/wp-includes/class-wp-post-type.php
@@ -335,6 +335,16 @@ final class WP_Post_Type {
 	 */
 	public $rest_controller_class;
 
+	/**
+	 * The controller instance for this post type's REST API endpoints.
+	 *
+	 * Lazily computed. Should be accessed using {@see WP_Post_Type::get_rest_controller()}.
+	 *
+	 * @since 5.3.0
+	 * @var WP_REST_Controller $rest_controller
+	 */
+	private $rest_controller;
+
 	/**
 	 * Constructor.
 	 *
@@ -682,4 +692,36 @@ final class WP_Post_Type {
 	public function remove_hooks() {
 		remove_action( 'future_' . $this->name, '_future_post_hook', 5 );
 	}
+
+	/**
+	 * Gets the REST API controller for this post type.
+	 *
+	 * Will only instantiate the controller class once per request.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @return WP_REST_Controller|null The controller instance, or null if the post type
+	 *                                 is set not to show in rest.
+	 */
+	public function get_rest_controller() {
+		if ( ! $this->show_in_rest ) {
+			return null;
+		}
+
+		$class = $this->rest_controller_class ? $this->rest_controller_class : WP_REST_Posts_Controller::class;
+
+		if ( ! class_exists( $class ) ) {
+			return null;
+		}
+
+		if ( ! is_subclass_of( $class, WP_REST_Controller::class ) ) {
+			return null;
+		}
+
+		if ( ! $this->rest_controller ) {
+			$this->rest_controller = new $class( $this->name );
+		}
+
+		return $this->rest_controller;
+	}
 }
diff --git a/wp-includes/rest-api.php b/wp-includes/rest-api.php
index a0bb8fba3a..c397bdc116 100644
--- a/wp-includes/rest-api.php
+++ b/wp-includes/rest-api.php
@@ -192,13 +192,9 @@ function rest_api_default_filters() {
  */
 function create_initial_rest_routes() {
 	foreach ( get_post_types( array( 'show_in_rest' => true ), 'objects' ) as $post_type ) {
-		$class = ! empty( $post_type->rest_controller_class ) ? $post_type->rest_controller_class : 'WP_REST_Posts_Controller';
+		$controller = $post_type->get_rest_controller();
 
-		if ( ! class_exists( $class ) ) {
-			continue;
-		}
-		$controller = new $class( $post_type->name );
-		if ( ! is_subclass_of( $controller, 'WP_REST_Controller' ) ) {
+		if ( ! $controller ) {
 			continue;
 		}
 
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php
index 7b2e4b223c..a72541a1ee 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php
@@ -59,11 +59,13 @@ class WP_REST_Autosaves_Controller extends WP_REST_Revisions_Controller {
 	public function __construct( $parent_post_type ) {
 		$this->parent_post_type = $parent_post_type;
 		$post_type_object       = get_post_type_object( $parent_post_type );
+		$parent_controller      = $post_type_object->get_rest_controller();
 
-		// Ensure that post type-specific controller logic is available.
-		$parent_controller_class = ! empty( $post_type_object->rest_controller_class ) ? $post_type_object->rest_controller_class : 'WP_REST_Posts_Controller';
+		if ( ! $parent_controller ) {
+			$parent_controller = new WP_REST_Posts_Controller( $parent_post_type );
+		}
 
-		$this->parent_controller    = new $parent_controller_class( $post_type_object->name );
+		$this->parent_controller    = $parent_controller;
 		$this->revisions_controller = new WP_REST_Revisions_Controller( $parent_post_type );
 		$this->rest_namespace       = 'wp/v2';
 		$this->rest_base            = 'autosaves';
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
index f2ead89ea0..0320efaae9 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
@@ -1592,8 +1592,14 @@ class WP_REST_Comments_Controller extends WP_REST_Controller {
 	 * @return bool Whether post can be read.
 	 */
 	protected function check_read_post_permission( $post, $request ) {
-		$posts_controller = new WP_REST_Posts_Controller( $post->post_type );
 		$post_type        = get_post_type_object( $post->post_type );
+		$posts_controller = $post_type->get_rest_controller();
+
+		// Ensure the posts controller is specifically a WP_REST_Posts_Controller instance
+		// before using methods specific to that controller.
+		if ( ! $posts_controller instanceof WP_REST_Posts_Controller ) {
+			$posts_controller = new WP_REST_Posts_Controller( $post->post_type );
+		}
 
 		$has_password_filter = false;
 
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 d355c3d076..4a00336e34 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
@@ -16,6 +16,14 @@
  */
 class WP_REST_Posts_Controller extends WP_REST_Controller {
 
+	/**
+	 * Instances of post type controllers keyed by post type.
+	 *
+	 * @since 5.3.0
+	 * @var WP_REST_Controller[]
+	 */
+	private static $post_type_controllers = array();
+
 	/**
 	 * Post type.
 	 *
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
index 97c677d27c..9edf6eced6 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
@@ -49,11 +49,15 @@ class WP_REST_Revisions_Controller extends WP_REST_Controller {
 	 */
 	public function __construct( $parent_post_type ) {
 		$this->parent_post_type  = $parent_post_type;
-		$this->parent_controller = new WP_REST_Posts_Controller( $parent_post_type );
 		$this->namespace         = 'wp/v2';
 		$this->rest_base         = 'revisions';
 		$post_type_object        = get_post_type_object( $parent_post_type );
 		$this->parent_base       = ! empty( $post_type_object->rest_base ) ? $post_type_object->rest_base : $post_type_object->name;
+		$this->parent_controller = $post_type_object->get_rest_controller();
+
+		if ( ! $this->parent_controller ) {
+			$this->parent_controller = new WP_REST_Posts_Controller( $parent_post_type );
+		}
 	}
 
 	/**
diff --git a/wp-includes/version.php b/wp-includes/version.php
index ad45e1fb25..3d62d06cd4 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-46271';
+$wp_version = '5.3-alpha-46272';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.