The Niger River (//; French: (le) fleuve Niger, pronounced ) is the principal river of West Africa, extending about 4,180 km (2,600 mi). Its drainage basin is 2,117,700 km2 (817,600 sq mi) in area. Its source is in the Guinea Highlands in southeastern Guinea. It runs in a crescent through Mali, Niger, on the border with Benin and then through Nigeria, discharging through a massive delta, known as the Niger Delta or the Oil Rivers, into the Gulf of Guinea in the Atlantic Ocean. The Niger is the third-longest river in Africa, exceeded only by the Nile and the Congo River (also known as the Zaïre River). Its main tributary is the Benue River.
The Niger has different names in the different languages of the region:
The earliest use of the name "Niger" for the river is by Leo Africanus in his Della descrittione dell’Africa et delle cose notabili che iui sono published in Italian in 1550. The name may come from Berber phrase ger-n-ger meaning "river of rivers". As Timbuktu was the southern end of the principal Trans-Saharan trade route to the western Mediterranean, it was the source of most European knowledge of the region.
Medieval European maps applied the name Niger to the middle reaches of the river, in modern Mali, but Quorra (Kworra) to the lower reaches in modern Nigeria, as these were not recognized at the time as being the same river. When European colonial powers began to send ships along the west coast of Africa in the 16th and 17th centuries, the Senegal River was often postulated to be the seaward end of the Niger. The Niger Delta, pouring into the Atlantic through mangrove swamps and thousands of distributaries along more than 160 kilometres (100 miles), was thought to be no more than coastal wetlands. It was only with the 18th-century visits of Mungo Park, who travelled down the Niger River and visited the great Sahelian empires of his day, that Europeans correctly identified the course of the Niger and extended the name to its entire course.
The modern nations of Nigeria and Niger take their names from the river, marking contesting national claims by colonial powers of the "Upper", "Lower" and "Middle" Niger river basin during the Scramble for Africa at the end of the 19th century.
The Niger River is a relatively "clear" river, carrying only a tenth as much sediment as the Nile because the Niger's headwaters lie in ancient rocks that provide little silt. Like the Nile, the Niger floods yearly; this begins in September, peaks in November, and finishes by May.
An unusual feature of the river is the Inner Niger Delta, which forms where its gradient suddenly decreases. The result is a region of braided streams, marshes, and lakes the size of Belgium; the seasonal floods make the Delta extremely productive for both fishing and agriculture.