diff --git a/lib/block-template-utils.php b/lib/block-template-utils.php
new file mode 100644
index 00000000000000..a644047d3cfdc1
--- /dev/null
+++ b/lib/block-template-utils.php
@@ -0,0 +1,114 @@
+<?php
+/**
+ * Utilities used to fetch and create templates and template parts.
+ *
+ * @package gutenberg
+ */
+
+/**
+ * Creates an export of the current templates and
+ * template parts from the site editor at the
+ * specified path in a ZIP file.
+ *
+ * @since 5.9.0
+ * @since 6.0.0 Adds the whole theme to the export archive.
+ *
+ * @global string $wp_version The WordPress version string.
+ *
+ * @return WP_Error|string Path of the ZIP file or error on failure.
+ */
+function gutenberg_generate_block_templates_export_file() {
+	global $wp_version;
+
+	if ( ! class_exists( 'ZipArchive' ) ) {
+		return new WP_Error( 'missing_zip_package', __( 'Zip Export not supported.', 'gutenberg' ) );
+	}
+
+	$obscura    = wp_generate_password( 12, false, false );
+	$theme_name = basename( get_stylesheet() );
+	$filename   = get_temp_dir() . $theme_name . $obscura . '.zip';
+
+	$zip = new ZipArchive();
+	if ( true !== $zip->open( $filename, ZipArchive::CREATE | ZipArchive::OVERWRITE ) ) {
+		return new WP_Error( 'unable_to_create_zip', __( 'Unable to open export file (archive) for writing.', 'gutenberg' ) );
+	}
+
+	$zip->addEmptyDir( 'templates' );
+	$zip->addEmptyDir( 'parts' );
+
+	// Get path of the theme.
+	$theme_path = wp_normalize_path( get_stylesheet_directory() );
+
+	// Create recursive directory iterator.
+	$theme_files = new RecursiveIteratorIterator(
+		new RecursiveDirectoryIterator( $theme_path ),
+		RecursiveIteratorIterator::LEAVES_ONLY
+	);
+
+	// Make a copy of the current theme.
+	foreach ( $theme_files as $file ) {
+		// Skip directories as they are added automatically.
+		if ( ! $file->isDir() ) {
+			// Get real and relative path for current file.
+			$file_path     = wp_normalize_path( $file );
+			$relative_path = substr( $file_path, strlen( $theme_path ) + 1 );
+
+			if ( ! wp_is_theme_directory_ignored( $relative_path ) ) {
+				$zip->addFile( $file_path, $relative_path );
+			}
+		}
+	}
+
+	// Load templates into the zip file.
+	$templates = gutenberg_get_block_templates();
+	foreach ( $templates as $template ) {
+		$template->content = traverse_and_serialize_blocks(
+			parse_blocks( $template->content ),
+			'_remove_theme_attribute_from_template_part_block'
+		);
+
+		$zip->addFromString(
+			'templates/' . $template->slug . '.html',
+			$template->content
+		);
+	}
+
+	// Load template parts into the zip file.
+	$template_parts = gutenberg_get_block_templates( array(), 'wp_template_part' );
+	foreach ( $template_parts as $template_part ) {
+		$zip->addFromString(
+			'parts/' . $template_part->slug . '.html',
+			$template_part->content
+		);
+	}
+
+	// Load theme.json into the zip file.
+	$tree = WP_Theme_JSON_Resolver_Gutenberg::get_theme_data( array(), array( 'with_supports' => false ) );
+	// Merge with user data.
+	$tree->merge( WP_Theme_JSON_Resolver_Gutenberg::get_user_data() );
+
+	$theme_json_raw = $tree->get_data();
+	// If a version is defined, add a schema.
+	if ( $theme_json_raw['version'] ) {
+		$theme_json_version = 'wp/' . substr( $wp_version, 0, 3 );
+		$schema             = array( '$schema' => 'https://schemas.wp.org/' . $theme_json_version . '/theme.json' );
+		$theme_json_raw     = array_merge( $schema, $theme_json_raw );
+	}
+
+	// Convert to a string.
+	$theme_json_encoded = wp_json_encode( $theme_json_raw, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE );
+
+	// Replace 4 spaces with a tab.
+	$theme_json_tabbed = preg_replace( '~(?:^|\G)\h{4}~m', "\t", $theme_json_encoded );
+
+	// Add the theme.json file to the zip.
+	$zip->addFromString(
+		'theme.json',
+		$theme_json_tabbed
+	);
+
+	// Save changes to the zip file.
+	$zip->close();
+
+	return $filename;
+}
diff --git a/lib/class-wp-rest-edit-site-export-controller-gutenberg.php b/lib/class-wp-rest-edit-site-export-controller-gutenberg.php
new file mode 100644
index 00000000000000..b05de230dd0ccd
--- /dev/null
+++ b/lib/class-wp-rest-edit-site-export-controller-gutenberg.php
@@ -0,0 +1,46 @@
+<?php
+/**
+ * Controller which provides REST endpoint for exporting current templates
+ * and template parts.
+ *
+ * This class extension exists so that theme exporting takes into account any updates/changes to
+ * WP_Theme_JSON_Gutenberg, WP_Theme_JSON_Resolver_Gutenberg or related classes.
+ *
+ * @package    gutenberg
+ * @subpackage REST_API
+ * @since 5.9.0
+ */
+
+if ( class_exists( 'WP_REST_Edit_Site_Export_Controller_Gutenberg' ) ) {
+	return;
+}
+
+class WP_REST_Edit_Site_Export_Controller_Gutenberg extends WP_REST_Edit_Site_Export_Controller {
+	/**
+	 * Output a ZIP file with an export of the current templates
+	 * and template parts from the site editor, and close the connection.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @return WP_Error|void
+	 */
+	public function export() {
+		// Generate the export file.
+		$filename = gutenberg_generate_block_templates_export_file();
+
+		if ( is_wp_error( $filename ) ) {
+			$filename->add_data( array( 'status' => 500 ) );
+
+			return $filename;
+		}
+
+		$theme_name = basename( get_stylesheet() );
+		header( 'Content-Type: application/zip' );
+		header( 'Content-Disposition: attachment; filename=' . $theme_name . '.zip' );
+		header( 'Content-Length: ' . filesize( $filename ) );
+		flush();
+		readfile( $filename );
+		unlink( $filename );
+		exit;
+	}
+}
diff --git a/lib/load.php b/lib/load.php
index b00c024778b5ff..f30f0900558611 100644
--- a/lib/load.php
+++ b/lib/load.php
@@ -53,6 +53,7 @@ function gutenberg_is_experiment_enabled( $name ) {
 
 	// Plugin specific code.
 	require_once __DIR__ . '/class-wp-rest-global-styles-controller-gutenberg.php';
+	require_once __DIR__ . '/class-wp-rest-edit-site-export-controller-gutenberg.php';
 	require_once __DIR__ . '/rest-api.php';
 
 	// Experimental.
@@ -204,6 +205,7 @@ function gutenberg_is_experiment_enabled( $name ) {
 require __DIR__ . '/demo.php';
 require __DIR__ . '/experiments-page.php';
 require __DIR__ . '/interactivity-api.php';
+require __DIR__ . '/block-template-utils.php';
 if ( gutenberg_is_experiment_enabled( 'gutenberg-full-page-client-side-navigation' ) ) {
 	require __DIR__ . '/experimental/full-page-client-side-navigation.php';
 }
diff --git a/lib/rest-api.php b/lib/rest-api.php
index 04f521d132c461..fedd75151584d5 100644
--- a/lib/rest-api.php
+++ b/lib/rest-api.php
@@ -18,3 +18,15 @@ function gutenberg_register_global_styles_endpoints() {
 	$global_styles_controller->register_routes();
 }
 add_action( 'rest_api_init', 'gutenberg_register_global_styles_endpoints' );
+
+if ( ! function_exists( 'gutenberg_register_edit_site_export_controller_endpoints' ) ) {
+	/**
+	 * Registers the Edit Site Export REST API routes.
+	 */
+	function gutenberg_register_edit_site_export_controller_endpoints() {
+		$edit_site_export_controller = new WP_REST_Edit_Site_Export_Controller_Gutenberg();
+		$edit_site_export_controller->register_routes();
+	}
+}
+
+add_action( 'rest_api_init', 'gutenberg_register_edit_site_export_controller_endpoints' );