| Lev Dyomin | |
| Type: | Cosmonaut |
| Nationality: | Soviet |
| Birth Date: | 11 January 1926 |
| Birth Place: | Moscow, Russian SFSR, Soviet Union |
| Death Place: | Zvyozdny Gorodok, Russia |
| Occupation: | Pilot |
| Rank: | Colonel, Soviet Air Force |
| Selection: | Air Force Group 2 |
| Time: | 2d 00h 12m |
| Mission: | Soyuz 15 |
| Awards: | Hero of the Soviet Union |
| Birth Name: | Lev Stepanovich Dyomin |
Lev Stepanovich Dyomin (; 11 January 1926 – 18 December 1998[1]) 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.
Dyomin was born in Moscow. He gained a doctoral degree in engineering from the Soviet Air Force Engineering Academy and the rank of Colonel in the Soviet Air Force.[1]
Aged 48 at the time of his flight on Soyuz 15, he was the oldest cosmonaut up to that point as well as the first grandfather to go into space. He remained in the program until leaving in 1982 to pursue deep-sea research. Dyomin died of cancer, in Zvyozdny Gorodok, in 1998.[1]
He was awarded: