Cape Breton South is a former provincial electoral district in Nova Scotia, Canada which existed from 1933 to 2013. It elected one member of the Nova Scotia House of Assembly. In its last configuration, the district included Sydney and its western suburbs until the North West Arm and south along the Sydney River until Blacketts Lake.
In 1933, the Cape Breton County was divided into five electoral districts, one of which was named Cape Breton South. In 2003, it lost part of the Ashby area to Cape Breton Nova and gained Balls Creek and the Coxheath area. Following the 2012 electoral boundary review, the district was dissolved into Northside-Westmount, Sydney-Whitney Pier and Sydney River-Mira-Louisbourg.
The electoral district was represented by the following members of the Legislative Assembly: