The Buryats joined the Russian state in the middle of the 17th century and were already formed into an independent people. The article deals with the problem of forming a group of Selenga Buryats as part of the Buryat people, which was formed on the basis of combining eight Mongolian genera and six Buryat genera from Pre-Baikal territory. Keywords: Mongolian clans, Shert, Selenga Buryats, Songols, Cossacks, taisha, Zaisan, Shulenga, steppe dumas, Lama. The Buryat people were formed on the basis of the consolidation of four Mongolian-speaking tribes: Khori, Ekhirits, Bulagats, Khongodors and the so-called Selenga Buryat group. The first three tribes originally lived on the territory near Lake Baikal, the Khongodors arrived in Buryatia from Mongolia in the XVII century. These tribes are relatively homogeneous ethnic groups. Unlike them, the Selenga Buryats are not an ethnic concept, but a geographical one. The Selenga Buryat group represents a very diverse ethnic picture, consisting of fragments of numerous tribes that came from the Mongolian steppes and the western shore of Lake Baikal. They are natives of eight western (Naiman baruun) genera of Mongolia: atagans, Asheabagats, Sartuly, Tabanguts, tsongols, udzons, Khatagins, podgorodnye, and six eastern (zuun zurgaan) genera of Pre-Baikal Territory, which include Haranut, Alaguevsky, Babai-Khuramshinsky, Gotol-Bumalsky, Olzonovsky, and Chinoyevsky. The most numerous genera that came from Mongolia were the Tabanguts, Songols (Tsongols), as well as the Atagan, Sartul, and sub-urban genera. The Atagans came from Mongolia in two different groups: in 1631, the Atagans-Sharaites under the leadership of the Dalai Kuluk, and in 1665, forty Atagans and four Hotoktinans under the leadership of the brothers Chikir-Baras-bator and Khangin-tsolomkhoshuchi. In 1630, the Sartuly arrived in Jida in the number of only seven people led by Kulogi, then in the first quarter of the XVIII century, another 50 people arrived from Mongolia u ... Read more