The fauna of freshwater fish of the North-East of Russia, represented by 70 species and subspecies belonging to 30 genera and 16 families, was considered; of the total number of species, more than a third are found only in the rivers of the region and are not known in the adjacent regions of Siberia and the Far East. Characteristics of classes, orders, families and genera of fish, definitive tables of families, genera, species and subspecies are given.