Yuri Vasyliovych Kondratyuk (June 21, 1897 – 1942) was a follower, supporter and founder of cosmism, pioneer of astronautics and spaceflight. He was a theoretician and a visionary who, in the early 20th century, foresaw ways of reaching the Moon. He is generally credited with the authorship of the first known Lunar Orbit Rendezvous (LOR), a key concept for human landing on the Moon and returning to Earth, published in 1916. LOR was later used by the Apollo missions for human spaceflight to the Moon.
Kondratyuk used an adopted pseudonym, while his birth name was Oleksandr Hnatovych Shargei.