diff --git a/src/wp-admin/nav-menus.php b/src/wp-admin/nav-menus.php
index f70826f8ff..ed9d052333 100644
--- a/src/wp-admin/nav-menus.php
+++ b/src/wp-admin/nav-menus.php
@@ -354,7 +354,13 @@ switch ( $action ) {
 
 			// Update menu items.
 			if ( ! is_wp_error( $_menu_object ) ) {
-				$messages = array_merge( $messages, wp_nav_menu_update_menu_items( $nav_menu_selected_id, $nav_menu_selected_title ) );
+				$messages = array_merge( $messages, wp_nav_menu_update_menu_items( $_nav_menu_selected_id, $nav_menu_selected_title ) );
+
+				// If the menu ID changed, redirect to the new URL.
+				if ( $nav_menu_selected_id != $_nav_menu_selected_id ) {
+					wp_redirect( admin_url( 'nav-menus.php?menu=' . intval( $_nav_menu_selected_id ) ) );
+					exit();
+				}
 			}
 		}
 		break;
diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index a1c9c97335..46fafc18b3 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -330,6 +330,7 @@ add_filter( 'determine_current_user', 'wp_validate_logged_in_cookie', 20 );
 // Split term updates.
 add_action( 'split_shared_term', '_wp_check_split_default_terms',  10, 4 );
 add_action( 'split_shared_term', '_wp_check_split_terms_in_menus', 10, 4 );
+add_action( 'split_shared_term', '_wp_check_split_nav_menu_terms', 10, 4 );
 
 /**
  * Filters formerly mixed into wp-includes
diff --git a/src/wp-includes/nav-menu.php b/src/wp-includes/nav-menu.php
index 29666f079b..9eb101933c 100644
--- a/src/wp-includes/nav-menu.php
+++ b/src/wp-includes/nav-menu.php
@@ -315,6 +315,8 @@ function wp_update_nav_menu_object( $menu_id = 0, $menu_data = array() ) {
 	if ( is_wp_error( $update_response ) )
 		return $update_response;
 
+	$menu_id = (int) $update_response['term_id'];
+
 	/**
 	 * Fires after a navigation menu has been successfully updated.
 	 *
diff --git a/src/wp-includes/taxonomy.php b/src/wp-includes/taxonomy.php
index c2d0acc307..8e3e03d8d5 100644
--- a/src/wp-includes/taxonomy.php
+++ b/src/wp-includes/taxonomy.php
@@ -4395,6 +4395,34 @@ function _wp_check_split_terms_in_menus( $term_id, $new_term_id, $term_taxonomy_
 	}
 }
 
+/**
+ * If the term being split is a nav_menu, change associations.
+ *
+ * @ignore
+ * @since 4.3.0
+ *
+ * @global wpdb $wpdb
+ *
+ * @param int    $term_id          ID of the formerly shared term.
+ * @param int    $new_term_id      ID of the new term created for the $term_taxonomy_id.
+ * @param int    $term_taxonomy_id ID for the term_taxonomy row affected by the split.
+ * @param string $taxonomy         Taxonomy for the split term.
+ */
+function _wp_check_split_nav_menu_terms( $term_id, $new_term_id, $term_taxonomy_id, $taxonomy ) {
+	if ( 'nav_menu' !== $taxonomy ) {
+		return;
+	}
+
+	// Update menu locations.
+	$locations = get_nav_menu_locations();
+	foreach ( $locations as $location => $menu_id ) {
+		if ( $term_id == $menu_id ) {
+			$locations[ $location ] = $new_term_id;
+		}
+	}
+	set_theme_mod( 'nav_menu_locations', $locations );
+}
+
 /**
  * Get data about terms that previously shared a single term_id, but have since been split.
  *
diff --git a/tests/phpunit/tests/term/splitSharedTerm.php b/tests/phpunit/tests/term/splitSharedTerm.php
index 66fb8bc5b8..b5439ef099 100644
--- a/tests/phpunit/tests/term/splitSharedTerm.php
+++ b/tests/phpunit/tests/term/splitSharedTerm.php
@@ -195,6 +195,75 @@ class Tests_Term_SplitSharedTerm extends WP_UnitTestCase {
 		$this->assertEquals( $new_term_id, get_post_meta( $cat_menu_item, '_menu_item_object_id', true ) );
 	}
 
+	/**
+	 * @ticket 33187
+	 * @group navmenus
+	 */
+	public function test_nav_menu_locations_should_be_updated_on_split() {
+		global $wpdb;
+
+		$cat_term = wp_insert_term( 'Foo Menu', 'category' );
+		$shared_term_id = $cat_term['term_id'];
+
+		$nav_term_id = wp_create_nav_menu( 'Foo Menu' );
+		$nav_term = get_term( $nav_term_id, 'nav_menu' );
+
+		// Manually modify because shared terms shouldn't naturally occur.
+		$wpdb->update( $wpdb->term_taxonomy,
+			array( 'term_id' => $shared_term_id ),
+			array( 'term_taxonomy_id' => $nav_term->term_taxonomy_id )
+		);
+
+		set_theme_mod( 'nav_menu_locations', array( 'foo' => $shared_term_id ) );
+
+		// Splitsville.
+		$new_term_id = _split_shared_term( $shared_term_id, $nav_term->term_taxonomy_id );
+
+		$locations = get_nav_menu_locations();
+		$this->assertEquals( $new_term_id, $locations['foo'] );
+	}
+
+	/**
+	 * @ticket 33187
+	 * @group navmenus
+	 */
+	public function test_nav_menu_term_should_retain_menu_items_on_split() {
+		global $wpdb;
+
+		$cat_term = wp_insert_term( 'Foo Menu', 'category' );
+		$shared_term_id = $cat_term['term_id'];
+
+		$nav_term_id = wp_create_nav_menu( 'Foo Menu' );
+		$nav_term = get_term( $nav_term_id, 'nav_menu' );
+
+		// Manually modify because shared terms shouldn't naturally occur.
+		$wpdb->update( $wpdb->term_taxonomy,
+			array( 'term_id' => $shared_term_id ),
+			array( 'term_taxonomy_id' => $nav_term->term_taxonomy_id )
+		);
+
+		$t1 = wp_insert_term( 'Random term', 'category' );
+		$cat_menu_item = wp_update_nav_menu_item( $shared_term_id, 0, array(
+			'menu-item-type' => 'taxonomy',
+			'menu-item-object' => 'category',
+			'menu-item-object-id' => $t1['term_id'],
+			'menu-item-status' => 'publish'
+		) );
+
+		// Updating the menu will split the shared term.
+		$new_nav_menu_id = wp_update_nav_menu_object( $shared_term_id, array(
+			'description' => 'Updated Foo Menu',
+			'menu-name' => 'Updated Foo Menu',
+		) );
+
+		$menu = wp_get_nav_menu_object( $new_nav_menu_id );
+		$this->assertSame( 'Updated Foo Menu', $menu->name );
+		$this->assertSame( 'Updated Foo Menu', $menu->description );
+
+		$menu_items = wp_get_nav_menu_items( $new_nav_menu_id );
+		$this->assertEquals( array( $cat_menu_item ), wp_list_pluck( $menu_items, 'ID' ) );
+	}
+
 	public function test_wp_get_split_terms() {
 		$found = wp_get_split_terms( $this->terms['t1']['term_id'] );