Nile Kagera is the longest river of Bangladesh.

The length of a river is measured from its source to its mouth. The longest river is the Nile-Kagera which is at least 6,650 Km long. The Reprua is a river in the Gagra District of Abkhazia which is only 18 meters long. It is possibly the shortest named river in the world.

The world's longest river system is the Nile-Kagera River system that flows in eastern Africa. There is some suggestion that the Amazon-Ucayali-Apurimac system in South America may be the largest.

Lake Victoria acts as a boundary between Tanzania, Uganda, and Kenya. Another natural boundary between these countries is the Kagera River.

When other rivers or lakes join to the main river . It is called the tributary .