St Quintins Castle also known as Llanblethian Castle was built in the 12th century.
The castle is situated in Llanblethian village in the Vale of Glamorgan in Wales which sits upon the River Thaw. It makes up part of the community of Cowbridge. Cowbridge is a small market town.
The land of Llanblethian was given as a lordship to Herbert de St Quentin in 1102 by Robert Fitzhamon, the first Norman Lord of Glamorgan
Originally as many castles were then it would have been made mainly of wood.
The St Quentin family kept the lands until 1233 when the land was seized by Richard Siward.
In 1245 however, Richard De Clare sized the land back as part of the much larger areas of Glamorganshire.
It was substantially rebuilt around 1312 by Gilbert de Clare, Earl of Gloucester into a courtyard castle. however, Gilbert de Clare was killed at the Battle of Bannockburn (1314) and work on the castle seemingly came to an end at this time.
The castle afterwards lost its status and by the fifteenth century, the gatehouse was being used as a local prison.
It was recorded in 1741 as being ruinous but even so was still occupied in 1820 but abandoned shortly after.