The patterns of spatial variation in gastropod diversity in the waterbodies of western Siberia have been revealed. The highest species and generic diversity of freshwater gastropods is found in the waterbodies of the forest-steppe zone; from there, these parameters significantly decrease northwards, reaching their minimum beyond the polar circle. The proportion of gastropods of non-European origin increases in the same direction. The possible reasons for these changes in the spatial diversity of aquatic gastropods and the likely connections between the latitudinal variation of their diversity and the geological history and features of the relief of western Siberia are discussed. It is assumed that the forest-steppe zone of western Siberia is a local center of aquatic gastropod diversity.