A bunker buster is a guided bomb that is designed to penetrate layers of rock, earth, or concrete before exploding. It is a type of hard-target munition. One such device is the U.S. GBU-57 A/B Massive Ordnance Penetrator, a 30,000-pound (13,600-kilogram) bomb that can penetrate roughly 200 feet (60 meters) of solid concrete. The GBU-57 A/B is equipped with a void-sensing fuze that can detect when the weapon has reached an open space, such as an underground room or bunker, at which point the bomb detonates. The United States used the GBU-57 A/B in strikes on Iranian nuclear facilities during fighting between Israel and Iran in 2025.