BALLYCASTLE, urban district, Co. Antrim, Northern Ire land, on a bay of the same name opposite Rathlin island. Pop. (1926) 1,986. It is connected with the Northern Counties (Mid land) railway at Ballymoney by the Ballycastle light railway. The town consists of two divisions, about a quarter of a mile apart and connected by a fine avenue. Much money has been expended upon the pier and harbour, but the violence of the sea overthrew the one and the other became filled with sand. To the east of the town are the remains of Bonamargy abbey. Coal seams, formerly extensively worked, appear in the cliffs towards Fair Head, and the fisheries are important.