The Niger River (/ Ë n aɪ dÊ Ér / NY-jÉr; French: (le) fleuve Niger [(lÉ) flÅv niÊÉÊ]) is the main river of West Africa, extending about 4,180 kilometres (2,600 miles).Its drainage basin is 2,117,700 km 2 (817,600 sq mi) in area. [11] Its source is in the Guinea Highlands in south-eastern Guinea near the Sierra Leone border. [12] [13] It runs in a crescent shape through Mali, Niger