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. In 1648 Ivan Galkin founded an ostrog on the Barguzin.
In its middle part the river flows along the Barguzin Valley or Depression (Russian: Баргузинская котловина), which is 200 kilometres (120 mi) long and up to 35 kilometres (22 mi) wide and runs between the Barguzin Range (to the northwest) and Ikat Range (to the southeast). In the valley the river branches, loops, leaves old riverbeds, and creates a swampy water network with more than 1,000 lakes. In the valley is the Dzherga State Nature Preserve (Russian: Джергинский государственный природный заповедник) encompassing 2,387 square kilometres (922 sq mi).
The river also gave its name to a steady, strong wind on Baikal. The air flow rushes onto Baikal from the Barguzin Valley and blows across the lake at its middle, mostly for no longer than a day (starting at sunrise and ending by sunset). Usually it brings sunny weather. In Barguzin Bay it may be of hurricane strength, but its average speed is usually less than 20 m/s. The wind is commemorated in the Russian folk song about a runaway from the Akatuy katorga:
- Славное море - священный Байкал,
- Славный корабль - омулевая бочка.
- Эй, баргузин, пошевеливай вал,
- Молодцу плыть недалечко.
- The sacred Baikal is a glorious sea,
- An omul barrel is a glorious ship.
- Hey, barguzin, roll the wave
- It is not too far to sail for a daring fellow.
- Poetic translation:
- Glorious sea, sacred Baikal,
- Glorious boat, a barrel of cisco.
- Hey, Barguzin make the waves rise and fall!
- This young lad's ready to frisk-o!