The largest river in Nigeria is the River Niger. It is the principal river in West Africa, flowing over 4,180 km (2,600 miles) through five countries, including Nigeria, before emptying into the Atlantic Ocean. The River Niger is the third-longest river in Africa, after the Nile and the Congo rivers. It is a vital source of water for irrigation, fishing, transportation, and hydroelectric power generation in Nigeria and other countries it flows through.