Llantwit Major is a small coastal town and community in the Vale of Glamorgan, Wales, lying on the Bristol Channel coast. It is one of four towns in Vale of Glamorgan and the third largest by population (13,366 in 2001) after Barry and Penarth, and ahead of Cowbridge, which lies about 4.5 miles (7.2 km) to the northeast. The town centre of Llantwit Major lies about 9 miles (14 km) southeast of the centre of Bridgend, 10 miles (16 km) west of the centre of Barry, and about 15 miles (24 km) miles northwest of the centre of the Welsh capital of Cardiff which lies further to the east beyond Barry.
In Welsh, the town is named Llanilltud Fawr, after Saint Illtud, who came to the area from Brittany. He founded a monastery and the college attached to it, Cor Tewdws, which would grow into one of the most esteemed Christian colleges of the times. The monastery was destroyed by the Vikings in 987, but rebuilt in 1111, and continued to be a centre of learning until it closed in 1539 in the Dissolution of the Monasteries. The 13th century St Illtyd's Church, built near the ancient monastery, is a Grade I listed building and is one of the oldest parish churches in Wales. The modern town of Llantwit Major developed rapidly in the 20th century to accommodate for the Royal Air Force serviceman in the base built at nearby St Athan, but it retains its mediaeval feel with narrow cobbled streets and high walls and many old buildings, including a 15th-century town hall.