Castle Bay (Mi'kmawi'simk: Apji'jkmujue'katik; Gaelic; Scottish Gaelic: Bàgh a' Chaisteil) is a community in the Canadian province of Nova Scotia, located in the Cape Breton Regional Municipality on Cape Breton Island.
The original Mi'kmaq placename, Apji'jkmujue'katik, means, "place of the ducks."