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 (now a hotel), there in 1765.
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 (and claimed his life) in 1794.
The town takes its name from its location near the mouth of the river called the Water of Fleet which empties into Wigtown Bay at Fleet Bay, and its former role as the "Gait House" or "the House on the Road on the River Fleet" or toll booth of the late 18th century stagecoach route from Dumfries to Stranraer, now the A75 road. It was a haven along this route, and travellers would often stop in the area rather than furthering the journey at night due to the high numbers of bandits and highwaymen at the time.
The settlement of Anwoth is one mile (1.5 km) to the west of Gatehouse of Fleet; this is where Samuel Rutherford was minister from 1627 to 1636.