An Caisteal (English: The Castle) is a hill fort located on the island of Coll. This island is one of the islands which make up the Inner Hebrides located on the west coast of Scotland. The fort is located at grid reference NM17185815. Located 1,200 yards (1.1 km) to the north-east of An Caisteal is Dùn Foulag. Dùn Foulag, located at grid reference NM17505908, was once thought to be a dun, though it is now considered to be only a naturally rocky knoll.