The article deals with the fauna of aquatic snails (Gastropoda) of the Nature Reserve (Zapovednik) Malaya Sos'va (Russia, Western Siberia, Tyumen Region). It is the first review of the Zapovednik malacofauna ever published. 44 waterbodies of different types were sampled in August of 2014, 16 species of Gastropoda belonging to four families had been registered. The annotated check-list of species along with brief zoogeographic characteristics of the fauna are provided. The fauna of aquatic snails of the Malaya Sos'va is impowerished as compared to other regions of Western Siberia. The possible factors caused this low taxonomic richness are discussed.