Garthland Castle was a castle that was located near Garthland Mains, Stoneykirk, Rhins of Galloway, Wigtownshire, Dumfries and Galloway, Scotland. The castle was possibly built in AD1211, as a datestone bearing that date has been discovered within the Garthland Mains estate. It would appear that further extensions in AD1274 were undertaken, as another datestone has been re-used within the Garthland Mains estate. The castle was seat of the family of M'Dowall of Garthland, Barony of Garthland, Stoneykirk, Wigtownshire.