diff --git a/wp-includes/blocks.php b/wp-includes/blocks.php
index fdd9de9afff..efdd9b1b1aa 100644
--- a/wp-includes/blocks.php
+++ b/wp-includes/blocks.php
@@ -1518,6 +1518,83 @@ function traverse_and_serialize_block( $block, $pre_callback = null, $post_callb
 	);
 }
 
+/**
+ * Replaces patterns in a block tree with their content.
+ *
+ * @since 6.6.0
+ *
+ * @param array $blocks An array blocks.
+ *
+ * @return array An array of blocks with patterns replaced by their content.
+ */
+function resolve_pattern_blocks( $blocks ) {
+	static $inner_content;
+	// Keep track of seen references to avoid infinite loops.
+	static $seen_refs = array();
+	$i                = 0;
+	while ( $i < count( $blocks ) ) {
+		if ( 'core/pattern' === $blocks[ $i ]['blockName'] ) {
+			$attrs = $blocks[ $i ]['attrs'];
+
+			if ( empty( $attrs['slug'] ) ) {
+				++$i;
+				continue;
+			}
+
+			$slug = $attrs['slug'];
+
+			if ( isset( $seen_refs[ $slug ] ) ) {
+				// Skip recursive patterns.
+				array_splice( $blocks, $i, 1 );
+				continue;
+			}
+
+			$registry = WP_Block_Patterns_Registry::get_instance();
+			$pattern  = $registry->get_registered( $slug );
+
+			// Skip unknown patterns.
+			if ( ! $pattern ) {
+				++$i;
+				continue;
+			}
+
+			$blocks_to_insert   = parse_blocks( $pattern['content'] );
+			$seen_refs[ $slug ] = true;
+			$prev_inner_content = $inner_content;
+			$inner_content      = null;
+			$blocks_to_insert   = resolve_pattern_blocks( $blocks_to_insert );
+			$inner_content      = $prev_inner_content;
+			unset( $seen_refs[ $slug ] );
+			array_splice( $blocks, $i, 1, $blocks_to_insert );
+
+			// If we have inner content, we need to insert nulls in the
+			// inner content array, otherwise serialize_blocks will skip
+			// blocks.
+			if ( $inner_content ) {
+				$null_indices  = array_keys( $inner_content, null, true );
+				$content_index = $null_indices[ $i ];
+				$nulls         = array_fill( 0, count( $blocks_to_insert ), null );
+				array_splice( $inner_content, $content_index, 1, $nulls );
+			}
+
+			// Skip inserted blocks.
+			$i += count( $blocks_to_insert );
+		} else {
+			if ( ! empty( $blocks[ $i ]['innerBlocks'] ) ) {
+				$prev_inner_content          = $inner_content;
+				$inner_content               = $blocks[ $i ]['innerContent'];
+				$blocks[ $i ]['innerBlocks'] = resolve_pattern_blocks(
+					$blocks[ $i ]['innerBlocks']
+				);
+				$blocks[ $i ]['innerContent'] = $inner_content;
+				$inner_content               = $prev_inner_content;
+			}
+			++$i;
+		}
+	}
+	return $blocks;
+}
+
 /**
  * Given an array of parsed block trees, applies callbacks before and after serializing them and
  * returns their concatenated output.
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-block-patterns-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-block-patterns-controller.php
index d8f083924e0..c98b2a7c57c 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-block-patterns-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-block-patterns-controller.php
@@ -162,6 +162,12 @@ protected function migrate_pattern_categories( $pattern ) {
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function prepare_item_for_response( $item, $request ) {
+		// Resolve pattern blocks so they don't need to be resolved client-side
+		// in the editor, improving performance.
+		$blocks        = parse_blocks( $item['content'] );
+		$blocks        = resolve_pattern_blocks( $blocks );
+		$item['content'] = serialize_blocks( $blocks );
+
 		$fields = $this->get_fields_for_response( $request );
 		$keys   = array(
 			'name'          => 'name',
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php
index 0ac6c7de5a2..cbf0ee040a9 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php
@@ -668,6 +668,12 @@ protected function prepare_item_for_database( $request ) {
 	 * @return WP_REST_Response Response object.
 	 */
 	public function prepare_item_for_response( $item, $request ) {
+		// Resolve pattern blocks so they don't need to be resolved client-side
+		// in the editor, improving performance.
+		$blocks        = parse_blocks( $item->content );
+		$blocks        = resolve_pattern_blocks( $blocks );
+		$item->content = serialize_blocks( $blocks );
+
 		// Restores the more descriptive, specific name for use within this method.
 		$template = $item;
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 8855bd235df..afe1e0d261b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-58299';
+$wp_version = '6.6-alpha-58303';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.