We analyzed intraspecies genetic variability of the medicinal tinder bracket polypore, Fomes fomentarius, from the Asian part of Russia, including the Ural, Altai, Western Sayan, and Baikal regions. We used nuclear ribosomal DNA internal transcribed spacer (ITS) sequence data as a standard marker for fungal DNA barcoding. In the Asian part of Russia, lineage A occurs as sublineage A2, which differs from sublineage A1 by a single nucleotide insertion at ITS2.3. Sublineage A2 is distributed up to Lake Baikal in the Ural, Altai, and Western Sayan regions. It can be characterized as a Eurasian sublineage of F. fomentarius. Lineage B is also represented by 2 sublineages (B1 and B2), which differ from each other by nucleotide sequences at ITS2.1. Sublineage B1 is represented by a small group of isolates from Asia (Iran, China, Nepal, South Korea), whereas sublineage B2 mainly includes isolates from Europe (Great Britain, Italy, Latvia, Slovakia, Slovenia) and 2 separate samples from Asia (Iran, China); these locales compose the distribution area of F. fomentarius. In the Asian part of Russia, lineage B is represented by sublineage B2 found in the Southern Urals (at the border between Europe and Asia), which is the only area where sublineages A2 and B2 are present. These sublineages are characterized by different substrate spectra: sublineage A2 is predominantly associated with Betula spp. and rarely with Alnus and Larix trees, whereas sublineage B2 does not have a pronounced substrate preference and is found in basidiomes collected from Acer, Duschekia, Prunus, and Salix trees, but not Betula trees. In general, the spectrum of substrates for F. fomentarius lineages A and B in the Asian part of Russia corresponds to that in other parts of this polypore's distribution area. Data are needed on genetic intraspecies variability (polymorphism) in relation to pharmacological properties for further biotechnological cultivation and use of the medicinal fungus F. fomentarius.