Sully is a village in the community of Sully and Lavernock, in the Vale of Glamorgan, Wales, lying on the northern coast of the Bristol Channel, midway between the towns of Penarth and Barry and 7 miles southwest of the Welsh capital city of Cardiff.

The Vale of Glamorgan, locally referred to as The Vale, is a county borough in the south-east of Wales. It borders Bridgend County Borough to the west, Cardiff to the east, Rhondda Cynon Taf to the north, and the Bristol Channel to the south. With an economy based largely on agriculture and chemicals, it is the southernmost unitary authority in Wales. Attractions include Barry Island Pleasure Park, the Barry Tourist Railway, Medieval wall paintings in St Cadoc's Church, Llancarfan, Porthkerry Park, St Donat's Castle, Cosmeston Lakes Country Park and Cosmeston Medieval Village. The largest town is Barry. Other towns include Penarth, Llantwit Major, and Cowbridge. There are many villages in the county borough.