Konstantin Eduardovich Tsiolkovsky (; – 19 September 1935) was a Russian and Soviet rocket scientist who pioneered astronautics. Along with Robert Esnault-Pelterie, Hermann Oberth, Fritz von Opel and Robert H. Goddard, he is one of the founding fathers of modern rocketry and astronautics. His works later inspired leading Soviet rocket engineers Sergei Korolev and Valentin Glushko, who contributed to the success of the Soviet space program.
Tsiolkovsky spent most of his life in a log house on the outskirts of Kaluga, about southwest of Moscow. A recluse by nature, his unusual habits made him seem bizarre to his fellow townsfolk.
Tsiolkovsky was born in Izhevskoye (now in Spassky District, Ryazan Oblast), in the Russian Empire, to a middle-class family. His father, Makary Edward Erazm Ciołkowski, was a Polish forester of Roman Catholic faith who relocated to Russia; his Russian Orthodox mother was of mixed Volga Tatar and Russian origin. His father was successively a forester, teacher, and minor government official. At the age of 10, Konstantin caught scarlet fever and lost his hearing. When he was 13, his mother died. He was not admitted to elementary schools because of his hearing problem, so he was self-taught. As a reclusive home-schooled child, he passed much of his time by reading books and became interested in mathematics and physics. As a teenager, he began to contemplate the possibility of space travel.
Tsiolkovsky spent three years attending a Moscow library, where Russian cosmism proponent Nikolai Fyodorov worked. He later came to believe that colonizing space would lead to the perfection of the human species, with immortality and a carefree existence.
Additionally, inspired by the fiction of Jules Verne, Tsiolkovsky theorized many aspects of space travel and rocket propulsion. He is considered the father of spaceflight and the first person to conceive the space elevator, becoming inspired in 1895 by the newly constructed Eiffel Tower in Paris.