St Donat's Castle is a medieval castle in South Wales, overlooking the Bristol Channel in the village of St Donat's near Llantwit Major, and about 25km west of Cardiff. St.Donat's church lies close to the castle.
The castle lies on a promontory with precipitous cliffs on the west. An inner ward about 40m across with a polygonal wall is closely surrounded by an outer ward with a dry moat facing the eastern approach. The outer wall mostly survives and has a small original tower entirely contained with it on the north, and a square gatehouse on the east.
The inner ward is entered by an arch beside the rectangular Mansell Tower on the east side. The western part of the inner curtain is gone, making room for the early 16th century north and west ranges, and the remainder has buildings of various dates against both sides of it.
The late 15th-century hall lies on the south of the ward. Beside it, squeezed in between the inner and outer curtains, is the Bradenstoke Hall, a modern building re-using the early 14th-century roof. The Lady Ann tower southwest of this is also modern and on the west side of the castle is a large modern dining hall.
The earliest surviving parts of the castle were built in the late twelfth century by the de Hawey family. Ownership passed to the Stradling family in 1298 through the marriage of Sir Peter Stradling to Joan de Hawey.
The Stradling family (which included a notable recusant, a well-known antiquary and a Latin poet; an earlier Stradling heiress, also the subject of a particularly hyperbolic lamentation by the Welsh poet Tudur Aled) owned St Donat's Castle until the death of Thomas Stradling in 1738, when ownership of the castle was passed to John Tyrwhitt. Archbishop Ussher resided for a time during the Civil War.
Thereafter the castle fell into a state of disrepair until it was revitalised by newspaper magnate William Randolph Hearst in the late 1920s.
The castle now houses Atlantic College, a private international boarding school founded in 1962 as the first of the ten United World Colleges.
Within the castle grounds lies St Donat's Arts Centre, housed in a 14th century tythe barn which has been converted to a professionally equipped theatre, together with a contrasting new addition of the Glass Room. This is said to offer "stunning views across the sea towards Exmoor to create one of the most inspired and inspiring public buildings in Wales". The centre provides a varied programme of cinema, exhibitions, festivals and live shows.
St. Donat's Castle is reputed to be one of the most haunted places in Wales, and is associated with numerous tales of the supernatural. An exorcism was reportedly performed in the early 20th century, which succeeded in ridding the castle of several eldritch apparitions, including a hag and a mysterious yellow eye that was projected onto the ceilings of several guest rooms.