Gusinoozyorsk is a city, the administrative center of the Selenginsky District of Buryatia Republic in the Russian Federation.
It is located in the Gusinoozyorsky Hollow on the northeast shore of the Gusinoe Lake, 110 km to the southwest of Ulan-Ude on the Kyakhtinsky Highway A340, at the 6 km distance from the railway station of Zagustay.
The central part of the city settles down on southwest steppe of the Monosta Ridge of Selenginsky middle mountains.
The city has sharply continental climate. Winters are snowy and cold, with dry frosts, whereas summers are short and often hot. The average temperature is +19 ºÑ in summer, and −22 ºÑ in winter.
On the southwest shore of the Gusinoe Lake, in the same-name village, there is a Buddhist monastery named Gusinoozyorsky (Tamchinsky) Datsan that was founded in 1741. A branch of the datsan is located in the City Park of Gusinoozyorsk.