Castlereagh << KAS uhl RAY >> is a small townland (community) in eastern Northern Ireland. It lies southeast of Belfast and has become one of Belfast’s suburbs. Its name in Irish is An Caisleán Riabhach.
Castlereagh takes its name from a gray castle that once stood on a hill in the area. The castle was built and maintained by the Clannaboy (also spelled Clandeboye) line of the O’Neill family, who descended from some of the early high kings of Ireland. The O’Neills held vast estates in the Ulster province of Ireland until English forces made them leave the region in the early 1600’s. See Ireland, History of (The arrival of Celtic culture; The Irish recovery).
The Castlereagh area was once part of County Down, one of the six historic counties of Northern Ireland. The county ceased to be used as an administrative area in 1973, when local government was reorganized into smaller districts. From 1973 to 2015, Castlereagh was the name of a district council area—a kind of local government area—southeast of Belfast. In 2015, most of the Lisburn and Castlereagh districts were combined to form a single local government district called Lisburn and Castlereagh. A small part of each of the two former districts became part of the Belfast local government district.
