river in western Africa, rising in the uplands of northern Guinea, east of the Fouta Djallon massif, and flowing roughly north-northeast to enter Mali. It then turns northwest to form the Mali–Senegal border for the rest of its course to the Sénégal River, except for a slight detour across a corner of western Senegal. It is approximately 250 miles (400 km) long and, although interrupted by rapids, is partially navigable from July to September. Its basin has a high rainfall, and there is some alluvial gold along its valley. The major towns along the river are Satadougou (Mali) and Kidira (Senegal).