diff --git a/src/wp-includes/blocks/navigation.php b/src/wp-includes/blocks/navigation.php
index bbaa8794be985..be67f1ea4279c 100644
--- a/src/wp-includes/blocks/navigation.php
+++ b/src/wp-includes/blocks/navigation.php
@@ -147,7 +147,7 @@ function render_block_core_navigation( $attributes, $content, $block ) {
 
 	if ( ! empty( $block->context['navigationArea'] ) ) {
 		$area    = $block->context['navigationArea'];
-		$mapping = get_option( 'fse_navigation_areas', array() );
+		$mapping = _wp_get_navigation_areas_menus();
 		if ( ! empty( $mapping[ $area ] ) ) {
 			$attributes['navigationMenuId'] = $mapping[ $area ];
 		}
diff --git a/src/wp-includes/navigation-areas.php b/src/wp-includes/navigation-areas.php
index e2d7460c3815a..7bf10540cd8a3 100644
--- a/src/wp-includes/navigation-areas.php
+++ b/src/wp-includes/navigation-areas.php
@@ -78,7 +78,7 @@ function _wp_migrate_menu_to_navigation_post( $new_name, WP_Theme $new_theme, WP
 	add_filter( 'option_stylesheet', $get_old_theme_stylesheet );
 
 	$locations    = get_nav_menu_locations();
-	$area_mapping = get_option( 'fse_navigation_areas', array() );
+	$area_mapping = _wp_get_navigation_areas_menus();
 
 	foreach ( $locations as $location_name => $menu_id ) {
 		// Get the menu from the location, skipping if there is no
@@ -124,15 +124,38 @@ function _wp_migrate_menu_to_navigation_post( $new_name, WP_Theme $new_theme, WP
 				'post_status'  => 'publish',
 			);
 			$navigation_post_id      = wp_insert_post( $post_data );
+			// If wp_insert_post fails *at any time*, then bale out of the entire
+			// migration attempt returning the WP_Error object.
+			if ( is_wp_error( $navigation_post_id ) ) {
+				return $navigation_post_id;
+			}
 		}
 
 		$area_mapping[ $location_name ] = $navigation_post_id;
 	}
 	remove_filter( 'option_stylesheet', $get_old_theme_stylesheet );
 
-	update_option( 'fse_navigation_areas', $area_mapping );
+	update_option( 'wp_navigation_areas', $area_mapping );
 }
 
+/**
+ * Retrieves navigation areas.
+ *
+ * @return array Navigation areas.
+ */
+function _wp_get_navigation_areas_menus() {
+	$areas = get_option( 'wp_navigation_areas', array() );
+	if ( ! $areas ) {
+		// Original key used `fse` prefix but Core options should use `wp`.
+		// We fallback to the legacy option to catch sites with values in the
+		// original location.
+		$legacy_option_key = 'fse_navigation_areas';
+		$areas             = get_option( $legacy_option_key, array() );
+	}
+	return $areas;
+}
+
+
 /**
  * Returns the menu items for a WordPress menu location.
  *
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-block-navigation-areas-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-block-navigation-areas-controller.php
index ef515f5970615..cb3005ef83fc8 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-block-navigation-areas-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-block-navigation-areas-controller.php
@@ -177,9 +177,9 @@ public function get_item( $request ) {
 	public function update_item( $request ) {
 		$name = $request['area'];
 
-		$mapping          = get_option( 'fse_navigation_areas', array() );
+		$mapping          = _wp_get_navigation_areas_menus();
 		$mapping[ $name ] = $request['navigation'];
-		update_option( 'fse_navigation_areas', $mapping );
+		update_option( 'wp_navigation_areas', $mapping );
 
 		$area = $this->get_navigation_area_object( $name );
 		$data = $this->prepare_item_for_response( $area, $request );
@@ -196,7 +196,7 @@ public function update_item( $request ) {
 	 */
 	protected function get_navigation_area_object( $name ) {
 		$available_areas   = get_navigation_areas();
-		$mapping           = get_option( 'fse_navigation_areas', array() );
+		$mapping           = _wp_get_navigation_areas_menus();
 		$area              = new stdClass();
 		$area->name        = $name;
 		$area->navigation  = ! empty( $mapping[ $name ] ) ? $mapping[ $name ] : null;