The Isle of Doagh (also Doagh Isle) is a peninsula in the north west of Ireland, in County Donegal. It once was an island but as sea levels fell, it became joined to the mainland. The ruins of Carrickabraghy Castle stands at the north-western extremity of the peninsula.
Coordinates: 55°18′04″N 7°20′38″W / 55.301°N 7.344°W