| En Name: | Ust-Barguzin |
| Ru Name: | Усть-Баргузин |
| Loc Name1: | Баргажанай Адаг |
| Loc Lang1: | Buryat |
| Coordinates: | 53.4°N 111°W |
| Map Label Position: | bottom |
| Federal Subject: | Republic of Buryatia |
| Adm District Jur: | Barguzinsky District |
| Adm Selsoviet Jur: | Ust-Barguzin Urban-Type Settlement |
| Adm Selsoviet Type: | Urban-type settlement |
| Adm Ctr Of: | Ust-Barguzin Urban-Type Settlement |
| Inhabloc Cat: | Urban-type settlement |
| Mun District Jur: | Barguzinsky Municipal District |
| Urban Settlement Jur: | Ust-Barguzin Urban Settlement |
| Mun Admctr Of: | Ust-Barguzin Urban Settlement |
| Pop 2010Census: | 7173 |
| Established Date: | 1666 |
| Postal Codes: | 671623, 671624 |
| Ust-Barguzin population | |
| Label1: | 2010 Census |
| Data1: | 7,173 |
| Label2: | 2002 Census |
| Data2: | 7,329 |
| Label3: | 1989 Census |
| Data3: | 7,204 |
| Label4: | 1979 Census |
| Data4: | 7,338 |
Ust-Barguzin (Russian: Усть-Баргузи́н; Buriat: Баргажанай Адаг, Bargajanai Adag) is an urban locality (an urban-type settlement) in Barguzinsky District of the Republic of Buryatia, Russia, located on the shore of Lake Baikal at the mouth of the Barguzin River and 270km (170miles) northeast of Ulan-Ude, the capital of the republic. As of the 2010 Census, its population was 7,173.
It was founded in 1666 by a Cossack detachment under Gavril Lovzov.
Within the framework of administrative divisions, the urban-type settlement (inhabited locality) of Ust-Barguzin, together with eight rural localities, is incorporated within Barguzinsky District as Ust-Barguzin Urban-Type Settlement[1] (an administrative division of the district).[2] As a municipal division, Ust-Barguzin Urban-Type Settlement is incorporated within Barguzinsky Municipal District as Ust-Barguzin Urban Settlement.[3]
Ust-Barguzin has a subarctic climate (Köppen climate classification Dwc) with severely cold winters and mild summers. Precipitation is quite low and is significantly higher in summer than at other times of the year.