Sergey Aleksandrovich Volkov (Russian: ?????? ????????????? ??????; born April 1, 1973, in Chuhuiv, Ukrainian SSR, Soviet Union) is a retired Russian cosmonaut and engineer.
He was a member of three missions to the International Space Station, spending more than a year in total in space.
During his missions he did four spacewalks lasting more than 23 hours in total.
Volkov retired from the Cosmonaut group in February 2017.