Fouta Djallon or Futa Jallon (both: fōˈtä jälôNˈ) [key], highland region, c.30,000 sq mi (77,700 sq km), central Guinea, W Africa. Largely a rolling grassland (average alt. c.3,000 ft/910 m), the region is grazed by cattle of the Fulani. The Niger, Senegal, and Gambia rivers rise there. Since the 18th cent. it has been a stronghold of Islam.