The aimag is located in the extreme west of the country, and shares borders with both Russia and China. The border between the two neighbouring countries is very short here, though, and ends after about 40 km at the eastern end of Kazakhstan. Within Mongolia, the neighbouring aimags are Uvs in the north east and Khovd in the south east.
The country's only Muslimand Kazakhmajority aimag, it was established in August 1940. Its capital is Ölgii.
Bayan-Ölgii is the highest Mongolian aimag. For the most part it is located in the Mongolian Altay, at the transition point to the Russian Altay. About 10% of the territory are covered by forests, consisting primarily of Siberian Larch.
The Nairamdal Peak (also Friendship Peak, Chinese: Youyi Feng) of the Altai Tavan Bogd (five saints mountain) massif mountain marks the corner between the three neighbouring countries. About 2.5 km further south on the Mongolian-Chinese border, the Khüiten Peak is the highest point of Mongolia at a height of 4,374 m. The massif includes several glaciers, such as the 19 km Potanin Glacier, and is only accessible to experienced climbers with local guidance.