Castlereagh is located in Belfast city, United Kingdom at the 54.5735, -5.8847 coordinates. Distance from Castlereagh to other cities. are listed below, click on the city name to find distance between. Distance from Castlereagh to Londonderry County Borough 103 km, to Derry 103 km, to Lisburn 11 km. The green marker indicates the location of Castlereagh.