Sergey Aleksandrovich Volkov 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.

Expedition 17 was the 17th expedition to the International Space Station (ISS). The first two crew members, Sergey Volkov, and Oleg Kononenko were launched on 8 April 2008, aboard the Soyuz TMA-12. Once aboard the station, they joined Garrett Reisman, who transferred from Expedition 16 to join the Expedition 17 crew.