St Donat's Castle, St Donats, Wales, is a medieval castle in the Vale of Glamorgan, about 16 miles (26 km) to the west of Cardiff, and about 1+1⁄2 miles (2.4 km) to the west of Llantwit Major. Positioned on cliffs overlooking the Bristol Channel, the site has been occupied since the Iron Age, and was by tradition the home of the Celtic chieftain Caradog. The present castle's origins date from the 12th century when the de Haweys and later Peter de Stradling began its development. The Stradlings held the castle for four hundred years, until the death of Sir Thomas Stradling in a duel in 1738.

The Vale of Glamorgan, locally referred to as The Vale, is a county borough in the south-east of Wales. It borders Bridgend County Borough to the west, Cardiff to the east, Rhondda Cynon Taf to the north, and the Bristol Channel to the south. With an economy based largely on agriculture and chemicals, it is the southernmost unitary authority in Wales. Attractions include Barry Island Pleasure Park, the Barry Tourist Railway, Medieval wall paintings in St Cadoc's Church, Llancarfan, Porthkerry Park, St Donat's Castle, Cosmeston Lakes Country Park and Cosmeston Medieval Village. The largest town is Barry. Other towns include Penarth, Llantwit Major, and Cowbridge. There are many villages in the county borough.