Llantwit Major (Welsh: Llanilltud Fawr) is a town and community in Wales. Situated on the Bristol Channel coast, it is one of four towns in the Vale of Glamorgan, with the third largest population (13,366 in 2001) after Barry and Penarth, and ahead of Cowbridge. Llantwit Major is 4 1⁄2 miles (7.2 km) from Cowbridge, 9 miles (14 km) from Bridgend, 10 miles (16 km) from Barry, and 15 miles (24 km) from Cardiff. The community had a population of 9,486 in 2011.
Llanilltud Fawr is named for the Llan of Saint Illtud, the Llan was home to the Monastery of Illtud and the College known as Côr Tewdws. Llantwit would grow into one of the most esteemed centres of Christian culture in the Celtic world. At its peak it attracted over 2000 students, including princes, numerous eminent clergymen and revered saints. The institutions were destroyed by the raiding Vikings in 987, but the monastery was rebuilt by the Normans in 1111 and continued to be a centre of learning until it was disbanded in 1539 during the Dissolution of the Monasteries. The 13th-century St Illtyd's Church, built near the ancient monastery, is a Grade I listed building and one of the oldest parish churches in Wales.
In the 20th century, the modern town developed rapidly to accommodate Royal Air Force personnel from the St Athan base. The medieval cobbled streets and buildings of the 15th and 16th centuries remain.
Colhugh Beach is a popular surfing venue and has the remnants of an Iron Age fort and some of the finest examples of Jurassic Period fossils in Wales. The pebble beach and its clifftops are protected by the Glamorgan Heritage Coast, which stretches for 14 miles (23 km) from Gileston to the east to Southerndown and Newton Point to the west.