Garry Kasparov is a Soviet / Russian former World Chess Champion, regarded by many as the greatest chess player of all time. He is also a writer and political activist. Kasparov became the youngest ever undisputed World Chess Champion in 1985. He held the official FIDE world title until 1993, when a dispute with FIDE led him to set up a rival organization, the Professional Chess Association. He continued to hold the "Classical" World Chess Championship until his defeat by Vladimir Kramnik in 2000. Kasparov's ratings achievements include being rated world #1 according to Elo rating almost continuously from 1986 until his retirement in 2005 and holding the all-time highest rating of 2851. Source: Gary Kasparov's Chess Biography on Wikipedia.