Sergei Avdeyev, Russian engineer and astronaut
Sergei Vasilyevich Avdeyev (Сергей Васильевич Авдеев; born 1 January 1956) is a Russian engineer and cosmonaut.

Avdeyev was born in Chapayevsk, Samara Oblast (formerly Kuybyshev Oblast), Russian SFSR. He graduated from Moscow Engineering Physics Institute in 1979 as an engineer-physicist [1]. From 1979 to 1987 he worked as an engineer for NPO Energiya. He was selected as a cosmonaut as part of the Energia Engineer Group 9 on 26 March 1987. His basic cosmonaut training was from December 1987 through to July 1989. He retired as a cosmonaut on 14 February 2003.

Avdeyev at one point held the record for cumulative time spent in space with 747.59 days in Earth orbit, accumulated through three tours of duty aboard the Mir Space Station. He has orbited the Earth 11,968 times traveling about 515,000,000 kilometers. In August 2005, this record was taken by another cosmonaut, Sergei K. Krikalev; it has since been surpassed by several other cosmonauts and the current record of 879 days was set by Gennady Padalka in 2015.

Avdeyev is married with two children. He is an amateur radio operator, and his call sign is RV3DW.