Sergei Lvovich Sedov (1908–1937) was Leon Trotsky's younger son by his second wife, Natalia Sedova, and an engineer. He was allegedly killed in the Great Purges.Sedov was a Moscow-based engineer who published works on thermodynamics and diesel engines. He became a professor at the Moscow Institute of Technology while still in his twenties. Unlike his parents and his older brother Lev Sedov, Sergei Sedov was not active in politics.