The Congo is the largest river in Western Central Africa. Its overall length of 4,380 km (2,720 mi) makes it the second longest in Africa (after the Nile). If the Chambeshi River is taken as the source, the overall length increases to 4,670 km (2900 mi). The river and its tributaries flow through the second largest rain forest area in the world, only the Amazon Rainforest being (much) larger. The river also has the second-largest flow in the world, behind the Amazon, and the second-largest watershed of any river, again trailing the Amazon and slightly ahead of the Mississippi. The Congo also gives its name to the Democratic Republic of the Congo and the Republic of the Congo, both countries lying along its banks, and to the ancient Kingdom of Kongo. Between 1971 and 1997 the government of then-Zaire called it the Zaire River.
The sources of the Congo are in the highlands and mountains of the East Africa Rift, as well as Lake Tanganyika and Lake Mweru, which feed the Lualaba River, which then becomes the Congo below Boyoma Falls.
The Congo flows generally west from Kisangani just below the falls, then gradually bends southwest, passing by Mbandaka, joining with the Ubangi River, and running into the Pool Malebo (Stanley Pool).