Gatehouse of Fleet (Scots: Gatehoose o Fleet Scottish Gaelic: Taigh an Rathaid) is a town in the civil parish of Girthon, Kirkcudbrightshire, within the district council region of Dumfries and Galloway, Scotland, which has existed since the mid-18th century, although the area has been inhabited since much earlier. Much of its development was attributable to the entrepreneur James Murray's decision to build his summer home, Cally House there in 1763. The house is now the Cally Palace Hotel.
Over the next hundred years, the town developed into a centre for industry, particularly cotton mills. The western approach to the town is dominated by the imposing Cardoness Castle. Gatehouse of Fleet is the birthplace of Victorian artist John Faed. The renowned inventor of clockwork mechanisms, Robert Williamson, was also known to have set up a workshop in the town in 1778, which burned to the ground in 1794, killing him.