The Kagera River, also Akagera River, or Alexandra Nile, is an East African river, forming part of the upper headwaters of the Nile and carrying water from its most distant source.

The section of river named Kagera begins in Burundi, flowing out from Lake Rweru. From the lake, it flows east along the Rwanda-Burundi and Rwanda-Tanzania borders to a confluence with the Ruvubu River. The waters of the Kagera are thus provided by two major tributaries, the Nyabarongo of Rwanda, which feeds Lake Rweru, and the Ruvubu of Burundi. It is unknown which of these two feeder rivers is the longer and hence the ultimate source of the Nile. From the confluence, the Kagera flows north along the Rwanda-Tanzania border, over Rusumo Falls and through Akagera National Park. It then takes a turn to the east, following the Tanzania-Uganda border and emptying into Lake Victoria in Uganda.