Casamance (kăz´əmäns), river, c.200 mi (320 km) long, W Africa. It rises in S Senegal and flows westward, emptying in the Atlantic Ocean. The virtually unnavigable river lies in a region of lush floodplains between the enclave of The Gambia and Guinea-Bissau. Also called Casamance, the Senegalese region is geographically isolated from the rest of the country by The Gambia, and the Diola (or Jola), not the Wolof, are the primary ethnic group. Ziguinchor is the largest city in the region. Casamance was the scene of ethnic tensions and demonstrations for independence in the early 1980s, and guerrilla warfare beginning in the late 1980s. A cease-fire was signed with some of the rebels in 2004, but others have continued to fight. The Gambia and Guinea-Bissau have at times aided the rebels. In 2006 fighting erupted in neighboring Guinea-Bissau between Casamance rebels that had established bases there and Bissau troops. The name also appears as Kasamansa.