Fort Willem II of Ungaran (known locally as Benteng Ungaran or Benteng Diponegoro) is a late 18th-century Dutch-built fort located in Ungaran, in the Semarang Regency, Central Java, Indonesia. It was constructed to guard a trade route in central Java. The fort is the place where Prince Diponegoro was imprisoned while waiting for his judgment in Batavia and further exile to Makassar. The fort is currently used as a dormitory for the families of Indonesian police personnel.