Dassen Island is an uninhabited South African island in the Atlantic Ocean. It is situated about 10 km (6 mi) west of Yzerfontein and 55 km (34 mi) north of Cape Town. The flat and low-lying island measures about 3.1 km² (1.2 sq mi) long northwest-southeast and 1 km² (0.4 sq mi) wide, with an area of 2.73 km² (1.05 sq mi).