Cuanza Sul is a province of Angola. It has an area of 55,660 km² and a population of approximately 600,000. Sumbe is the capital of the province. Municipalities in this province include Porto Amboim, Seles, Conda, Amboim, Quilenda, Libolo, Mussende, Quibala, Waku-Kungo, Cassongue and Ebo.
Cuanza Sul lies on the south bank of the Cuanza River.