The Congo Basin is the sedimentary basin that is the drainage of the Congo River of west equatorial Africa. The basin begins in the highlands of the East African Rift system with input from the Chambeshi River, the Uele and Ubangi Rivers in the upper reaches and the Lualaba River draining wetlands in the middle reaches. Due to the young age and active uplift of the East African Rift at the headlands, the river's yearly sediment load is very large but the drainage basin occupies large areas of low relief throughout much of its area. The basin is a total of 3.7 million square kilometers and is home to some of the largest undisturbed stands of tropical rainforest on the planet, in addition to large wetlands. The basin ends where the river empties its load in the Gulf of Guinea on the Atlantic Ocean. The climate is equatorial tropical, with two rainy seasons including very high rainfalls, and high temperature year round. The basin is home to the endangered western lowland gorilla.

The basin was originally the watershed of the Congo River populated by pygmy peoples, but Bantus migrated there from West Africa and eventually founded the Kingdom of Kongo. Belgium, France, and Portugal later established colonial control over the entire region by the late 19th century.