According to archaeological, linguistic, ethnographic, and mythological evidence, the Buriat ethnic group arose from a blending of western Mongolian tribes (Oirot) with Turkish (Altai, northern Siberian) and Tungus groups and possibly even Samoyed peoples. The territory where the ancestors of the Buriats lived and where the nucleus of the Buriat people formed includes the regions along Lake Baikal, in particular Pribaikal'e, the island of Ol'khon, and part of the territories to the east along the Selenga River. To the north, the neighbors of the Buriats were the Evenki and Yakut and to the south and east, related Mongolian tribes. Toward the middle of the seventeenth century during the Russian conquest of Siberia, the Buriats divided themselves into several territorial tribal groups, the largest of which were the Bulugat, Ekhirit, and Khor (Khorint, Khori-Buriat). The Bulugat lived along the Angara River and its tributaries. The Ekhirit lived along the northern shores of Lake Baikal and in the valley of the Barguzin River. The Khorint settled in the upper reaches of the Lena River and on the island of Ol'khon, from where they gradually penetrated farther and farther to the east up to the Aga steppes (now Chita Oblast).
The Buriats are made up of several groups: Tubin (Soiot), Tyngyc (Evenk, Khamnigan), and those native to Mongolia (Khongodor, Sartyl, Tsongol, Tabangyt, and others). Some of these settled in the upper reaches of the Selenga and Dzhida rivers. In the 1660s Buriatia became part of the Russian state. After the October Revolution of 1917, the Buriat-Mongol Autonomous Oblast was formed in 1921 within the Far Eastern Republic, and the Mongol-Buriat Autonomous Oblast was formed in 1922 within the Russian Sovied Federated Socialist Republic (RSFSR). In 1923 the Buriat-Mongol Autonomous Soviet Socialist Republic was united with the RSFSR, into which was also incorporated the former territory of Pribaikal'e Province with its Russian population. In 1958 it was renamed the Buriat Autonomous Soviet Socialist Republic.