Castletown (Manx: Balley Chashtal, pronounced [ˈbalʲə ˈxaʃtʃəl]) is a town geographically within the Malew parish of the Isle of Man but administered separately. Lying at the south of the island, it was the Manx capital until 1869. The centre of town is dominated by Castle Rushen, a well-preserved castle.

Castletown is the former capital of the Isle of Man and site of Tynwald, and can trace its roots back to 1090. The town has narrow streets and small fishing cottages. Fishing boats still continue to go out to fish from the harbour. Commercial traffic to the port ended in the 1970s, although there has been an ongoing expansion of finance and industrial businesses in the area. The first telephones appeared in Castletown in 1901.