diff --git a/wp-includes/class-wp-theme-json-resolver.php b/wp-includes/class-wp-theme-json-resolver.php
index 59c5f54b96..db3a48c5c8 100644
--- a/wp-includes/class-wp-theme-json-resolver.php
+++ b/wp-includes/class-wp-theme-json-resolver.php
@@ -744,4 +744,82 @@ class WP_Theme_JSON_Resolver {
 		}
 		return $variations;
 	}
+
+	/**
+	 * Resolves relative paths in theme.json styles to theme absolute paths
+	 * and returns them in an array that can be embedded
+	 * as the value of `_link` object in REST API responses.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param WP_Theme_JSON  $theme_json A theme json instance.
+	 * @return array An array of resolved paths.
+	 */
+	public static function get_resolved_theme_uris( $theme_json ) {
+		$resolved_theme_uris = array();
+
+		if ( ! $theme_json instanceof WP_Theme_JSON ) {
+			return $resolved_theme_uris;
+		}
+
+		$theme_json_data = $theme_json->get_raw_data();
+
+		// Top level styles.
+		$background_image_url = isset( $theme_json_data['styles']['background']['backgroundImage']['url'] ) ? $theme_json_data['styles']['background']['backgroundImage']['url'] : null;
+
+		/*
+		 * The same file convention when registering web fonts.
+		 * See: WP_Font_Face_Resolver:: to_theme_file_uri.
+		 */
+		$placeholder = 'file:./';
+		if (
+			isset( $background_image_url ) &&
+			is_string( $background_image_url ) &&
+			// Skip if the src doesn't start with the placeholder, as there's nothing to replace.
+			str_starts_with( $background_image_url, $placeholder )
+		) {
+			$file_type          = wp_check_filetype( $background_image_url );
+			$src_url            = str_replace( $placeholder, '', $background_image_url );
+			$resolved_theme_uri = array(
+				'name'   => $background_image_url,
+				'href'   => sanitize_url( get_theme_file_uri( $src_url ) ),
+				'target' => 'styles.background.backgroundImage.url',
+			);
+			if ( isset( $file_type['type'] ) ) {
+				$resolved_theme_uri['type'] = $file_type['type'];
+			}
+			$resolved_theme_uris[] = $resolved_theme_uri;
+		}
+
+		return $resolved_theme_uris;
+	}
+
+	/**
+	 * Resolves relative paths in theme.json styles to theme absolute paths
+	 * and merges them with incoming theme JSON.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param WP_Theme_JSON  $theme_json A theme json instance.
+	 * @return WP_Theme_JSON Theme merged with resolved paths, if any found.
+	 */
+	public static function resolve_theme_file_uris( $theme_json ) {
+		$resolved_urls = static::get_resolved_theme_uris( $theme_json );
+		if ( empty( $resolved_urls ) ) {
+			return $theme_json;
+		}
+
+		$resolved_theme_json_data = array(
+			'version' => WP_Theme_JSON::LATEST_SCHEMA,
+		);
+
+		foreach ( $resolved_urls as $resolved_url ) {
+			$path = explode( '.', $resolved_url['target'] );
+			_wp_array_set( $resolved_theme_json_data, $path, $resolved_url['href'] );
+		}
+
+		$theme_json->merge( new WP_Theme_JSON( $resolved_theme_json_data ) );
+
+		return $theme_json;
+	}
 }
diff --git a/wp-includes/global-styles-and-settings.php b/wp-includes/global-styles-and-settings.php
index fd1890c53a..fbf4fe2c52 100644
--- a/wp-includes/global-styles-and-settings.php
+++ b/wp-includes/global-styles-and-settings.php
@@ -139,6 +139,7 @@ function wp_get_global_styles( $path = array(), $context = array() ) {
  *
  * @since 5.9.0
  * @since 6.1.0 Added 'base-layout-styles' support.
+ * @since 6.6.0 Resolves relative paths in theme.json styles to theme absolute paths.
  *
  * @param array $types Optional. Types of styles to load.
  *                     It accepts as values 'variables', 'presets', 'styles', 'base-layout-styles'.
@@ -179,9 +180,9 @@ function wp_get_global_stylesheet( $types = array() ) {
 		}
 	}
 
-	$tree = WP_Theme_JSON_Resolver::get_merged_data();
-
+	$tree                = WP_Theme_JSON_Resolver::resolve_theme_file_uris( WP_Theme_JSON_Resolver::get_merged_data() );
 	$supports_theme_json = wp_theme_has_theme_json();
+
 	if ( empty( $types ) && ! $supports_theme_json ) {
 		$types = array( 'variables', 'presets', 'base-layout-styles' );
 	} elseif ( empty( $types ) ) {
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-controller.php
index e9d5006d53..3b2caf88fe 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-controller.php
@@ -289,6 +289,7 @@ class WP_REST_Global_Styles_Controller extends WP_REST_Posts_Controller {
 	 * Prepare a global styles config output for response.
 	 *
 	 * @since 5.9.0
+	 * @since 6.6.0 Added custom relative theme file URIs to `_links`.
 	 *
 	 * @param WP_Post         $post    Global Styles post object.
 	 * @param WP_REST_Request $request Request object.
@@ -298,8 +299,10 @@ class WP_REST_Global_Styles_Controller extends WP_REST_Posts_Controller {
 		$raw_config                       = json_decode( $post->post_content, true );
 		$is_global_styles_user_theme_json = isset( $raw_config['isGlobalStylesUserThemeJSON'] ) && true === $raw_config['isGlobalStylesUserThemeJSON'];
 		$config                           = array();
+		$theme_json                       = null;
 		if ( $is_global_styles_user_theme_json ) {
-			$config = ( new WP_Theme_JSON( $raw_config, 'custom' ) )->get_raw_data();
+			$theme_json = new WP_Theme_JSON( $raw_config, 'custom' );
+			$config     = $theme_json->get_raw_data();
 		}
 
 		// Base fields for every post.
@@ -341,6 +344,15 @@ class WP_REST_Global_Styles_Controller extends WP_REST_Posts_Controller {
 
 		if ( rest_is_field_included( '_links', $fields ) || rest_is_field_included( '_embedded', $fields ) ) {
 			$links = $this->prepare_links( $post->ID );
+
+			// Only return resolved URIs for get requests to user theme JSON.
+			if ( $theme_json ) {
+				$resolved_theme_uris = WP_Theme_JSON_Resolver::get_resolved_theme_uris( $theme_json );
+				if ( ! empty( $resolved_theme_uris ) ) {
+					$links['https://api.w.org/theme-file'] = $resolved_theme_uris;
+				}
+			}
+
 			$response->add_links( $links );
 			if ( ! empty( $links['self']['href'] ) ) {
 				$actions = $this->get_available_actions( $post, $request );
@@ -515,6 +527,7 @@ class WP_REST_Global_Styles_Controller extends WP_REST_Posts_Controller {
 	 * Returns the given theme global styles config.
 	 *
 	 * @since 5.9.0
+	 * @since 6.6.0 Added custom relative theme file URIs to `_links`.
 	 *
 	 * @param WP_REST_Request $request The request instance.
 	 * @return WP_REST_Response|WP_Error
@@ -549,11 +562,15 @@ class WP_REST_Global_Styles_Controller extends WP_REST_Posts_Controller {
 		$response = rest_ensure_response( $data );
 
 		if ( rest_is_field_included( '_links', $fields ) || rest_is_field_included( '_embedded', $fields ) ) {
-			$links = array(
+			$links               = array(
 				'self' => array(
 					'href' => rest_url( sprintf( '%s/%s/themes/%s', $this->namespace, $this->rest_base, $request['stylesheet'] ) ),
 				),
 			);
+			$resolved_theme_uris = WP_Theme_JSON_Resolver::get_resolved_theme_uris( $theme );
+			if ( ! empty( $resolved_theme_uris ) ) {
+				$links['https://api.w.org/theme-file'] = $resolved_theme_uris;
+			}
 			$response->add_links( $links );
 		}
 
@@ -591,6 +608,7 @@ class WP_REST_Global_Styles_Controller extends WP_REST_Posts_Controller {
 	 *
 	 * @since 6.0.0
 	 * @since 6.2.0 Returns parent theme variations, if they exist.
+	 * @since 6.6.0 Added custom relative theme file URIs to `_links` for each item.
 	 *
 	 * @param WP_REST_Request $request The request instance.
 	 *
@@ -606,9 +624,24 @@ class WP_REST_Global_Styles_Controller extends WP_REST_Posts_Controller {
 			);
 		}
 
+		$response   = array();
 		$variations = WP_Theme_JSON_Resolver::get_style_variations();
 
-		return rest_ensure_response( $variations );
+		foreach ( $variations as $variation ) {
+			$variation_theme_json = new WP_Theme_JSON( $variation );
+			$resolved_theme_uris  = WP_Theme_JSON_Resolver::get_resolved_theme_uris( $variation_theme_json );
+			$data                 = rest_ensure_response( $variation );
+			if ( ! empty( $resolved_theme_uris ) ) {
+				$data->add_links(
+					array(
+						'https://api.w.org/theme-file' => $resolved_theme_uris,
+					)
+				);
+			}
+			$response[] = $this->prepare_response_for_collection( $data );
+		}
+
+		return rest_ensure_response( $response );
 	}
 
 	/**
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-revisions-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-revisions-controller.php
index 4a37f28d37..54285fa560 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-revisions-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-revisions-controller.php
@@ -268,6 +268,7 @@ class WP_REST_Global_Styles_Revisions_Controller extends WP_REST_Revisions_Contr
 	 * Prepares the revision for the REST response.
 	 *
 	 * @since 6.3.0
+	 * @since 6.6.0 Added resolved URI links to the response.
 	 *
 	 * @param WP_Post         $post    Post revision object.
 	 * @param WP_REST_Request $request Request object.
@@ -281,11 +282,13 @@ class WP_REST_Global_Styles_Revisions_Controller extends WP_REST_Revisions_Contr
 			return $global_styles_config;
 		}
 
-		$fields = $this->get_fields_for_response( $request );
-		$data   = array();
+		$fields     = $this->get_fields_for_response( $request );
+		$data       = array();
+		$theme_json = null;
 
 		if ( ! empty( $global_styles_config['styles'] ) || ! empty( $global_styles_config['settings'] ) ) {
-			$global_styles_config = ( new WP_Theme_JSON( $global_styles_config, 'custom' ) )->get_raw_data();
+			$theme_json           = new WP_Theme_JSON( $global_styles_config, 'custom' );
+			$global_styles_config = $theme_json->get_raw_data();
 			if ( rest_is_field_included( 'settings', $fields ) ) {
 				$data['settings'] = ! empty( $global_styles_config['settings'] ) ? $global_styles_config['settings'] : new stdClass();
 			}
@@ -322,11 +325,21 @@ class WP_REST_Global_Styles_Revisions_Controller extends WP_REST_Revisions_Contr
 			$data['parent'] = (int) $parent->ID;
 		}
 
-		$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
-		$data    = $this->add_additional_fields_to_object( $data, $request );
-		$data    = $this->filter_response_by_context( $data, $context );
+		$context             = ! empty( $request['context'] ) ? $request['context'] : 'view';
+		$data                = $this->add_additional_fields_to_object( $data, $request );
+		$data                = $this->filter_response_by_context( $data, $context );
+		$response            = rest_ensure_response( $data );
+		$resolved_theme_uris = WP_Theme_JSON_Resolver::get_resolved_theme_uris( $theme_json );
 
-		return rest_ensure_response( $data );
+		if ( ! empty( $resolved_theme_uris ) ) {
+			$response->add_links(
+				array(
+					'https://api.w.org/theme-file' => $resolved_theme_uris,
+				)
+			);
+		}
+
+		return $response;
 	}
 
 	/**
diff --git a/wp-includes/version.php b/wp-includes/version.php
index b20be4fbd2..7e457609ff 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-58261';
+$wp_version = '6.6-alpha-58262';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.