Mikhail Moiseyevich Botvinnik was a Soviet and Russian chess grandmaster who held five world titles in three different reigns. The sixth World Chess Champion, he also worked as an electrical engineer and computer scientist and was a pioneer in computer chess. He also had a mathematics degree (honorary).
Botvinnik in 1962
Botvinnik in 1927
Botvinnik vs. Lasker, 1936
Levenfish vs. Botvinnik (right), 1937
Grandmaster (GM) is a title awarded to chess players by the world chess organization FIDE. Apart from World Champion, Grandmaster is the highest title a chess player can attain. Once achieved, the title is held for life, though exceptionally the title can be revoked for cheating.
Siegbert Tarrasch (1862–1934)
Akiba Rubinstein (1880–1961)
Jacques Mieses (1865–1954), one of the first FIDE Grandmasters