Aimags of Mongolia in the context of Districts of Mongolia

Bayan-Ölgii (/ˈbaɪən ˈoʊlɡi/ BY-ən OHL-gee) is the westernmost of the 21 aimags (provinces) of Mongolia. The country's only Muslim and Kazakh-majority aimag, it was established in August 1940, having its capital at Ölgii.

The Great Lakes Depression, also called the Great Lakes Hollow, is a large semi-arid depression in Mongolia that covers parts of the Uvs, Khovd, Bayan-Ölgii, Zavkhan and Govi-Altai aimags. Bounded by the Altai in the West, Khangai in the East and Tannu-Ola Mountains in the North,it covers the area of over 100,000 km (39,000 sq mi) with elevations from 750 to 2,000 m (2,460–6,560 ft).

Small northern parts of the depression are part of Russia.

Khovd (/kɒvd/; Mongolian: Ховд [ˈχɔɸt]), alternatively romanized as Khobhd, is one of the twenty-one aimags (provinces) of Mongolia, located in the west of the country. Its capital is also named Khovd. Khovd province is approximately 1,580 km (980 mi) from Ulaanbaatar, Mongolia's capital. It takes its name from the Khovd River, which is located in this province.

Islam is a significant religion practiced by around 10–15% of the population, namely the Kazakhs and a small minority of Uyghurs.

Selenge (Mongolian: Сэлэнгэ) is one of the 21 aimags (provinces) of Mongolia, located in the north of the country, directly bordering Russia. It lies in the broad, fertile river basins of the Selenge and Orkhon rivers, which are among Mongolia's most important waterways. The name is derived from the Selenge river. The capital is Sükhbaatar.

The province of Darkhan-Uul, and its capital Darkhan, is an enclave inside Selenge.