Llantwit Major is a town and community in Wales on the Bristol Channel coast. It is one of four towns in the Vale of Glamorgan, with the third largest population after Barry and Penarth, and ahead of Cowbridge. It 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. It had a population of 9,530 in 2021.

The Bristol Channel is a major inlet in the island of Great Britain, separating South Wales and South West England. It extends from the smaller Severn Estuary of the River Severn to the North Atlantic Ocean. It takes its name from the English city and port of Bristol.