Lev Stepanovich Demin (born January 11 1926 in Moscow, died December 18, 1998 in Zvyozdny Gorodok) was a Soviet cosmonaut who flew on the Soyuz 15 mission.
Demin gained a doctoral degree in engineering from the Soviet Air Force Engineering Acadmeny and the rank of Colonel in the Soviet Air Force.
He only made a single spaceflight before resigning from the space programme in 1982 and taking up deep-sea research.
He died of cancer in 1998.