diff --git a/src/wp-includes/block-template-utils.php b/src/wp-includes/block-template-utils.php
index 2c2fd66d7c332..b0086f5d301fc 100644
--- a/src/wp-includes/block-template-utils.php
+++ b/src/wp-includes/block-template-utils.php
@@ -454,6 +454,39 @@ function _inject_theme_attribute_in_block_template_content( $template_content )
 	return $template_content;
 }
 
+/**
+ * Parses a block template and removes the theme attribute from each template part.
+ *
+ * @access private
+ * @since 5.9.0
+ *
+ * @param string $template_content Serialized block template content.
+ * @return string Updated block template content.
+ */
+function _remove_theme_attribute_in_block_template_content( $template_content ) {
+	$has_updated_content = false;
+	$new_content         = '';
+	$template_blocks     = parse_blocks( $template_content );
+
+	$blocks = _flatten_blocks( $template_blocks );
+	foreach ( $blocks as $key => $block ) {
+		if ( 'core/template-part' === $block['blockName'] && isset( $block['attrs']['theme'] ) ) {
+			unset( $blocks[ $key ]['attrs']['theme'] );
+			$has_updated_content = true;
+		}
+	}
+
+	if ( ! $has_updated_content ) {
+		return $template_content;
+	}
+
+	foreach ( $template_blocks as $block ) {
+		$new_content .= serialize_block( $block );
+	}
+
+	return $new_content;
+}
+
 /**
  * Build a unified template object based on a theme file.
  *
@@ -863,3 +896,55 @@ function block_header_area() {
 function block_footer_area() {
 	block_template_part( 'footer' );
 }
+
+/**
+ * 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
+ *
+ * @return WP_Error|string Path of the ZIP file or error on failure.
+ */
+function wp_generate_block_templates_export_file() {
+	if ( ! class_exists( 'ZipArchive' ) ) {
+		return new WP_Error( __( 'Zip Export not supported.' ) );
+	}
+
+	$obscura  = wp_generate_password( 12, false, false );
+	$filename = get_temp_dir() . 'edit-site-export-' . $obscura . '.zip';
+
+	$zip = new ZipArchive();
+	if ( true !== $zip->open( $filename, ZipArchive::CREATE ) ) {
+		return new WP_Error( __( 'Unable to open export file (archive) for writing.' ) );
+	}
+
+	$zip->addEmptyDir( 'theme' );
+	$zip->addEmptyDir( 'theme/templates' );
+	$zip->addEmptyDir( 'theme/parts' );
+
+	// Load templates into the zip file.
+	$templates = get_block_templates();
+	foreach ( $templates as $template ) {
+		$template->content = _remove_theme_attribute_in_block_template_content( $template->content );
+
+		$zip->addFromString(
+			'theme/templates/' . $template->slug . '.html',
+			$template->content
+		);
+	}
+
+	// Load template parts into the zip file.
+	$template_parts = get_block_templates( array(), 'wp_template_part' );
+	foreach ( $template_parts as $template_part ) {
+		$zip->addFromString(
+			'theme/parts/' . $template_part->slug . '.html',
+			$template_part->content
+		);
+	}
+
+	// Save changes to the zip file.
+	$zip->close();
+
+	return $filename;
+}
diff --git a/src/wp-includes/rest-api.php b/src/wp-includes/rest-api.php
index 25f23fae64396..9617c81c91d99 100644
--- a/src/wp-includes/rest-api.php
+++ b/src/wp-includes/rest-api.php
@@ -349,6 +349,10 @@ function create_initial_rest_routes() {
 	// Menu Locations.
 	$controller = new WP_REST_Menu_Locations_Controller();
 	$controller->register_routes();
+
+	// Site Editor Export.
+	$controller = new WP_REST_Edit_Site_Export_Controller();
+	$controller->register_routes();
 }
 
 /**
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-edit-site-export-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-edit-site-export-controller.php
new file mode 100644
index 0000000000000..1bd40cd637c14
--- /dev/null
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-edit-site-export-controller.php
@@ -0,0 +1,93 @@
+<?php
+/**
+ * REST API: WP_REST_Edit_Site_Export_Controller class
+ *
+ * @package    WordPress
+ * @subpackage REST_API
+ */
+
+/**
+ * Controller which provides REST endpoint for exporting current templates
+ * and template parts.
+ *
+ * @since 5.9.0
+ *
+ * @see WP_REST_Controller
+ */
+class WP_REST_Edit_Site_Export_Controller extends WP_REST_Controller {
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 5.9.0
+	 */
+	public function __construct() {
+		$this->namespace = 'wp-block-editor/v1';
+		$this->rest_base = 'export';
+	}
+
+	/**
+	 * Registers the site export route.
+	 *
+	 * @since 5.9.0
+	 */
+	public function register_routes() {
+		register_rest_route(
+			$this->namespace,
+			'/' . $this->rest_base,
+			array(
+				array(
+					'methods'             => WP_REST_Server::READABLE,
+					'callback'            => array( $this, 'export' ),
+					'permission_callback' => array( $this, 'permissions_check' ),
+				),
+			)
+		);
+	}
+
+	/**
+	 * Checks whether a given request has permission to export.
+	 *
+	 * @since 5.9.0
+	 *
+	 * @return WP_Error|true True if the request has access, or WP_Error object.
+	 */
+	public function permissions_check() {
+		if ( ! current_user_can( 'edit_theme_options' ) ) {
+			new WP_Error(
+				'rest_cannot_view_url_details',
+				__( 'Sorry, you are not allowed to export templates and template parts.' ),
+				array( 'status' => rest_authorization_required_code() )
+			);
+		}
+
+		return true;
+	}
+
+	/**
+	 * 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 = wp_generate_block_templates_export_file();
+
+		if ( is_wp_error( $filename ) ) {
+			$filename->add_data( array( 'status' => 500 ) );
+
+			return $filename;
+		}
+
+		header( 'Content-Type: application/zip' );
+		header( 'Content-Disposition: attachment; filename=edit-site-export.zip' );
+		header( 'Content-Length: ' . filesize( $filename ) );
+		flush();
+		readfile( $filename );
+		unlink( $filename );
+		exit;
+	}
+}
diff --git a/src/wp-settings.php b/src/wp-settings.php
index 3b0e179baf149..85b2f2146a680 100644
--- a/src/wp-settings.php
+++ b/src/wp-settings.php
@@ -275,6 +275,7 @@
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-themes-controller.php';
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-plugins-controller.php';
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-block-directory-controller.php';
+require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-edit-site-export-controller.php';
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php';
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-application-passwords-controller.php';
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-site-health-controller.php';
diff --git a/tests/phpunit/tests/block-template-utils.php b/tests/phpunit/tests/block-template-utils.php
index 930735c72fd6a..fc382862a89c4 100644
--- a/tests/phpunit/tests/block-template-utils.php
+++ b/tests/phpunit/tests/block-template-utils.php
@@ -189,6 +189,38 @@ function test_inject_theme_attribute_in_block_template_content() {
 		$this->assertSame( $content_with_no_template_part, $template_content );
 	}
 
+	/**
+	 * @ticket 54448
+	 *
+	 * @dataProvider data_remove_theme_attribute_in_block_template_content
+	 */
+	function test_remove_theme_attribute_in_block_template_content( $template_content, $expected ) {
+		$this->assertEquals( $expected, _remove_theme_attribute_in_block_template_content( $template_content ) );
+	}
+
+	function data_remove_theme_attribute_in_block_template_content() {
+		return array(
+			array(
+				'<!-- wp:template-part {"slug":"header","theme":"tt1-blocks","align":"full","tagName":"header","className":"site-header"} /-->',
+				'<!-- wp:template-part {"slug":"header","align":"full","tagName":"header","className":"site-header"} /-->',
+			),
+			array(
+				'<!-- wp:group --><!-- wp:template-part {"slug":"header","theme":"tt1-blocks","align":"full","tagName":"header","className":"site-header"} /--><!-- /wp:group -->',
+				'<!-- wp:group --><!-- wp:template-part {"slug":"header","align":"full","tagName":"header","className":"site-header"} /--><!-- /wp:group -->',
+			),
+			// Does not modify content when there is no existing theme attribute.
+			array(
+				'<!-- wp:template-part {"slug":"header","align":"full","tagName":"header","className":"site-header"} /-->',
+				'<!-- wp:template-part {"slug":"header","align":"full","tagName":"header","className":"site-header"} /-->',
+			),
+			// Does not remove theme when there is no template part.
+			array(
+				'<!-- wp:post-content /-->',
+				'<!-- wp:post-content /-->',
+			),
+		);
+	}
+
 	/**
 	 * Should retrieve the template from the theme files.
 	 */
@@ -311,4 +343,37 @@ function test_flatten_blocks() {
 		$expected                     = array( $blocks[0] );
 		$this->assertSame( $expected, $actual );
 	}
+
+	/**
+	 * Should generate block templates export file.
+	 *
+	 * @ticket 54448
+	 */
+	function test_wp_generate_block_templates_export_file() {
+		$filename = wp_generate_block_templates_export_file();
+		$this->assertFileExists( $filename, 'zip file is created at the specified path' );
+		$this->assertTrue( filesize( $filename ) > 0, 'zip file is larger than 0 bytes' );
+
+		// Open ZIP file and make sure the directories exist.
+		$zip = new ZipArchive();
+		$zip->open( $filename );
+		$has_theme_dir                = $zip->locateName( 'theme/' ) !== false;
+		$has_block_templates_dir      = $zip->locateName( 'theme/templates/' ) !== false;
+		$has_block_template_parts_dir = $zip->locateName( 'theme/parts/' ) !== false;
+		$this->assertTrue( $has_theme_dir, 'theme directory exists' );
+		$this->assertTrue( $has_block_templates_dir, 'theme/templates directory exists' );
+		$this->assertTrue( $has_block_template_parts_dir, 'theme/parts directory exists' );
+
+		// ZIP file contains at least one HTML file.
+		$has_html_files = false;
+		$num_files      = $zip->numFiles;
+		for ( $i = 0; $i < $num_files; $i++ ) {
+			$filename = $zip->getNameIndex( $i );
+			if ( '.html' === substr( $filename, -5 ) ) {
+				$has_html_files = true;
+				break;
+			}
+		}
+		$this->assertTrue( $has_html_files, 'contains at least one html file' );
+	}
 }
diff --git a/tests/qunit/fixtures/wp-api-generated.js b/tests/qunit/fixtures/wp-api-generated.js
index 346645b7c568b..d6e11af97316f 100644
--- a/tests/qunit/fixtures/wp-api-generated.js
+++ b/tests/qunit/fixtures/wp-api-generated.js
@@ -10642,6 +10642,27 @@ mockedApiResponse.Schema = {
                     }
                 }
             ]
+        },
+        "/wp-block-editor/v1/export": {
+            "namespace": "wp-block-editor/v1",
+            "methods": [
+                "GET"
+            ],
+            "endpoints": [
+                {
+                    "methods": [
+                        "GET"
+                    ],
+                    "args": []
+                }
+            ],
+            "_links": {
+                "self": [
+                    {
+                        "href": "http://example.org/index.php?rest_route=/wp-block-editor/v1/export"
+                    }
+                ]
+            }
         }
     },
     "site_logo": 0,