Leonid Denisovich Kizim was born on August 5, 1941, in Krasny Lyman, Donetsk Oblast, Ukrainian SSR. He graduated from the Kachinsk Air Force Pilot School in 1963 and later from the Gagarin Air Force Academy in 1969. Kizim served as a pilot and flight instructor in the Soviet Air Force, eventually achieving the rank of Colonel-General. Selected as a cosmonaut in 1965, he flew on three space missions: Soyuz T-3, Soyuz T-10, and Soyuz T-15. Over his career, he logged 374 days, 17 hours, and 56 minutes in space, contributing significantly to long-duration spaceflight research. Kizim retired from the cosmonaut corps in 1987 and later worked in various capacities within the Russian space program until his death on June 14, 2010.