diff --git a/lib/class-wp-theme-json-resolver.php b/lib/class-wp-theme-json-resolver.php
index 31ecb553a2ccd0..afeee40d754b7f 100644
--- a/lib/class-wp-theme-json-resolver.php
+++ b/lib/class-wp-theme-json-resolver.php
@@ -402,7 +402,17 @@ public static function get_merged_data( $theme_support_data = array(), $origin =
 			$result->merge( self::get_user_data() );
 		}
 
-		return $result;
+		/**
+		 * Return merged data.
+		 *
+		 * @param array   $theme_support_data Existing block editor settings.
+		 * @param string  $origin             The source of data the consumer wants.
+		 *                                    Valid values are 'core', 'theme', 'user'.
+		 *                                    Default is 'user'.
+		 *
+		 * @return WP_Theme_JSON
+		 */
+		return apply_filters( 'global_styles_get_data', $result, $theme_support_data, $origin );
 	}
 
 	/**
diff --git a/lib/global-styles.php b/lib/global-styles.php
index 4bef8e7b93751c..38b514660c565c 100644
--- a/lib/global-styles.php
+++ b/lib/global-styles.php
@@ -10,7 +10,7 @@
  * the corresponding stylesheet.
  *
  * @param WP_Theme_JSON $tree Input tree.
- * @param string        $type Type of stylesheet we want accepts 'all', 'block_styles', and 'css_variables'.
+ * @param string        $type Type of stylesheet we want. Accepts 'all', 'block_styles', and 'css_variables'.
  *
  * @return string Stylesheet.
  */
@@ -28,7 +28,8 @@ function gutenberg_experimental_global_styles_get_stylesheet( $tree, $type = 'al
 		// Check if we have the styles already cached.
 		$cached = get_transient( 'global_styles' );
 		if ( $cached ) {
-			return $cached;
+			/* This filter is documented in lib/global-styles.php */
+			return apply_filters( 'global_styles_get_stylesheet', $cached, $type, $tree );
 		}
 	}
 
@@ -49,7 +50,16 @@ function gutenberg_experimental_global_styles_get_stylesheet( $tree, $type = 'al
 		set_transient( 'global_styles', $stylesheet, MINUTE_IN_SECONDS );
 	}
 
-	return $stylesheet;
+	/**
+	 * Filter generated styles.
+	 *
+	 * @param string        $stylesheet The generated styles.
+	 * @param string        $type       Type of stylesheet we want. Accepts 'all', 'block_styles', and 'css_variables'.
+	 * @param WP_Theme_JSON $tree       Input tree.
+	 *
+	 * @return string
+	 */
+	return apply_filters( 'global_styles_get_stylesheet', $stylesheet, $type, $tree );
 }
 
 /**