Castlereagh Area B was one of the three district electoral areas in Castlereagh, Northern Ireland which existed from 1973 to 1985. The district elected eight members to Castlereagh Borough Council, and formed part of the Belfast East constituencies for the Northern Ireland Assembly and UK Parliament.
It was created for the 1973 local elections, and contained the wards of Ballyhanwood, Carrowreagh, Dundonald, Enler, Gilnahirk, Lower Braniel, Tullycarnet and Upper Braniel. It was abolished for the 1985 local elections and replaced by the Castlereagh East DEA.