Lake Tanganyika is an African Great Lake. It is the second-oldest freshwater lake in the world, the second-largest by volume, and the second deepest, in all cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. The lake is shared among four countries—Tanzania, the Democratic Republic of the Congo, Burundi, and Zambia—with Tanzania (46%) and the DRC (40%) possessing the majority of the lake. It drains into the Congo River system and ultimately into the Atlantic Ocean.

The African Great Lakes are a series of lakes constituting the part of the Rift Valley lakes in and around the East African Rift. The series includes Lake Victoria, the third-largest freshwater lake in the world by area; Lake Tanganyika, the world's second-largest freshwater lake by volume and depth; Lake Malawi, the world's eighth-largest freshwater lake by area; and Lake Turkana, the world's largest permanent desert lake and the world's largest alkaline lake. Collectively, they contain 31,000 km3 (7,400 cu mi) of water, which is more than either Lake Baikal or the North American Great Lakes. This total constitutes about 25% of the planet's unfrozen surface fresh water. The large rift lakes of Africa are the ancient home of great biodiversity, and 10% of the world's fish species live in this region.