Bayan-Ovoo ( is a sum (district) of Khentii Province in eastern Mongolia. The sum had a population in 2008 of 1,581 and an area of 3,381 kmò.
Bayan-Ovoo has a continental climate (Köppen climate classification Dwb) with warm summers and severely cold winters. Most precipitation falls in the summer as rain, with some snow in autumn and spring. Winters are quite dry, with occasional light snow.
The district is divided into four bags, which are: