A new species of the genus Stigmaeus Koch, 1836 (Acari: Stigmaeidae), S. tolstikovi sp. nov. is described from rotten log of poplar from Western Siberia, Russia. Stigmaeus delaramae Khanjani, 2014 is recorded for the first time from Russia. Stigmaeus livschitzi Kuznetsov, 1977, S. longipilis (Canestrini, 1889), S. sphagneti (Hull, 1918), S. purpurascens Summers, 1962, and S. silvestris Khaustov, 2014 are recorded for the first time in Asian part of Russia. Stigmaeus livschitzi is redescribed based on study of type material. The key to species of the genus Stigmaeus of Russia is provided.