Barguzin (Russian: Баргузи́н; Buryat: Баргажан Bargažan) is a river in Buryatia, Russia, 480 kilometres (300 mi) long, flowing into the Barguzin Bay of Lake Baikal, the largest and deepest bay of Baikal. Barguzin is the third (by the flow amount) inflow of Baikal, after Selenga and Upper Angara River. Its watershed area is 21,100 square kilometres (8,100 sq mi). It is navigable for 204 kilometres (127 mi) upwards from its estuary. Its main tributaries are the Gagra, Argada, Ina, and Ulyun rivers.