|Full name||Gennadi Borisovich Sosonko|
|Country||Soviet Union (before 1972)|
Netherlands (after 1972)
|Born||May 18, 1943|
Troitsk, Russian SFSR, Soviet Union
|FIDE rating||2520 (November 2019)|
|Peak rating||2595 (January 1981)|
At the beginning of his career, in 1958, he won the Leningrad juniors championship.
Sosonko legally emigrated from the Soviet Union to the Netherlands via Israel in 1972.
He won the Dutch Championship in 1973 and 1978 (jointly). His tournament record includes 1st at Wijk aan Zee 1977, 1st at Nijmegen 1978, 3rd at Amsterdam 1980, 1st at Wijk aan Zee 1981, 3rd at Tilburg 1982 and 4th at Haninge 1988. He also drew a match with Jan Timman (+1 =0 −1) in 1984.
Sosonko played for the Dutch team at the Chess Olympiads eleven times, in 1974-84, and 1988-96. He won two individual medals: gold at Haifa 1976, bronze at Nice 1974, and two team medals: silver at Haifa 1976, and bronze at Thessaloniki 1988.
Sosonko has authored six non-technical chess books centering heavily on his chess life in the Soviet Union and his relationships with and memories of both leading Soviet players and lesser-known characters in chess history.
- Sosonko, Genna (2001). Russian Silhouettes. New in Chess. ISBN 90-5691-078-7.
- Sosonko, Genna (2003). The Reliable Past. New in Chess. ISBN 90-5691-114-7.
- Sosonko, Genna (2006). Smart Chip from St. Petersburg: And Other Tales of a Bygone Chess Era. New in Chess. ISBN 90-5691-169-4.
- Sosonko, Genna (2013). The World Champions I Knew. New in Chess. ISBN 90-5691-418-9.
- Sosonko, Genna (2017). The Rise and Fall of David Bronstein. Elk and Ruby Publishing House. ISBN 59-5004-331-6.
- Sosonko, Genna (2018). Evil-Doer: Half a Century with Viktor Korchnoi. Elk and Ruby Publishing House. ISBN 59-5004-338-3.