Lev Stepanovich Dyomin (Russian: Лев Степанович Дёмин; January 11, 1926, in Moscow – December 18, 1998, in Zvyozdny Gorodok) was a Soviet cosmonaut who flew on the Soyuz 15 spaceflight in 1974. This spaceflight was intended to dock with the space station Salyut 3, but the docking failed.