Garry Kasparov was the World Chess Champion from 1985 to 2000. He is often cited as one of the strongest players in the history of the game, if not the strongest.
Garry Kasparov (born 1963) became, at age 22, the youngest world champion in chess history in 1985 by defeating then-champion Anatoly Karpov. In 1993, while still champion, he split from FIDE to form the PCA, which resulted in an era of two split world championships. Kasparov retained his own title until losing a match to challenger Vladimir Kramnik in 2000. Currently, Kasparov holds the record for the highest Elo rating ever achieved (2851).
He retired from professional chess in 2005, though he has remained active as a chess author, and at times as a coach to players such as Magnus Carlsen and Hikaru Nakamura. He also remains active in chess politics, having championing the failed candidacy of his lifetime rival Karpov for the FIDE presidency in 2010, and hinted at his own candidacy in the future.