The Niger River is the longest river in Africa, stretching over 4, 200 miles from its source in the Guinea Highlands to its delta in the Gulf of Guinea. It is a major tributary of the River Nile and is the third-longest river in the world. The Niger River is an important source of water for many countries in West Africa, including Nigeria, Mali, Niger, and Benin. It is also home to a variety of wildlife, including hippopotamuses, crocodiles, and fish.