Gambia, river, c.700 mi (1,130 km) long, rising on the Fouta Djallon, N Guinea, W Africa, and flowing generally northwest through SE Senegal then west, bisecting The Gambia, to the Atlantic Ocean at Banjul. It is navigable for the entire length of The Gambia oceangoing vessels can reach Georgetown, c.175 mi (280 km) upstream. The river is the chief transport artery of The Gambia and provides access to interior sections of Senegal and Guinea. In 1978, Senegal and The Gambia formed the Gambia River Development Organization (which was joined by Guinea in 1980) for the purpose of developing the rivers natural resources.