freshwater mussels are ecosystem engineers and keystone species in aquatic environments. Unfortunately, due to dramatic declines this fauna is among the most threatened globally. Here, we clarify the taxonomy and biogeography of Russian Unionidae species based on the most comprehensive multi-locus dataset sampled to date. We revise the distribution and assess the conservation status for each species. This fauna comprises 16 native species from 11 genera and 4 tribes: Anodonta, Pseudanodonta (Anodontini); Amuranodonta, Beringiana, Buldowskia, Cristaria, Sinanodonta (cristariini); Middendorffinaia, Nodularia, Unio (Unionini); and Lanceolaria (Lanceolariini). no countrylevel endemic species are known in Russia, except for Buldowskia suifunica that may also occur in china. Sinanodonta woodiana, a non-native species, was introduced from china. Russia comprises the northern parts of Western and Eastern Palearctic subregions. The first subregion with six species encompasses a huge area from the western boundary of Russia to the Lena Basin in Siberia. the second subregion with 10 species covers the Amur Basin, rivers east of the Lena Basin, coastal basins of the Japan Sea, and the North Pacific Islands. The fauna of Russia primarily includes widespread generalist species that are here considered Least concern (Lc). However, Buldowskia suifunica and Sinanodonta lauta have restricted distributions and are assessed here as Vulnerable (VU) and endangered (en), respectively. Freshwater mussels (order Unionida) are ecologically and economically important aquatic animals 1 that are sensitive to water pollution, habitat loss, climate changes, and other negative anthropogenic and natural impacts 2-4. These animals are widely distributed throughout Russia, representing keystone taxa in various water bodies of European Russia, Siberia, and the Russian Far East (mainland, Sakhalin, and Kurile Archipelago) 5. However, freshwater mussels are not known to occur in the Polar Urals, Yamal and Taymyr peninsulas, Arctic Ocean
