Garry Kimovich Kasparov (born 13 April 1963) is a Russian chess grandmaster, former World Chess Champion (1985–2000), political activist and writer. His peak FIDE chess rating of 2851, achieved in 1999, was the highest recorded until being surpassed by Magnus Carlsen in 2013. From 1984 until his retirement from regular competitive chess in 2005, Kasparov was ranked world no. 1 for a record 255 months overall. Kasparov also holds records for the most consecutive professional tournament victories (15) and Chess Oscars (11).

Kasparov became the youngest-ever undisputed world champion in 1985 at age 22 by defeating then-champion Anatoly Karpov. He defended the title against Karpov three times, in 1986, 1987 and 1990. Kasparov held the official FIDE world title until 1993, when a dispute with FIDE led him to set up a rival organisation, the Professional Chess Association. In 1997, he became the first world champion to lose a match to a computer under standard time controls when he was defeated by the IBM supercomputer Deep Blue in a highly publicised match. He continued to hold the "Classical" world title until his defeat by Vladimir Kramnik in 2000. Despite losing the PCA title, he continued winning tournaments and was the world's highest-rated player at the time of his official retirement. Kasparov coached Carlsen in 2009–10, during which time Carlsen rose to world no. 1. Kasparov stood unsuccessfully for FIDE president in 2013–2014.

Since retiring from chess, Kasparov has devoted his time to writing and politics. His book series My Great Predecessors, first published in 2003, details the history and games of the world champion chess players who preceded him. He formed the United Civil Front movement and was a member of The Other Russia, a coalition opposing the administration and policies of Vladimir Putin. In 2008, he announced an intention to run as a candidate in that year's Russian presidential race, but after encountering logistical problems in his campaign, for which he blamed "official obstruction", he withdrew. In the wake of the Russian mass protests that began in 2011, he announced in June 2013 that he had left Russia for the immediate future out of fear of persecution. Following his flight from Russia, he lived in New York City with his family. In 2014, he obtained Croatian citizenship and has maintained a residence in Podstrana near Split.

Kasparov is chairman of the Human Rights Foundation and chairs its International Council. In 2017, he founded the Renew Democracy Initiative (RDI), an American political organisation promoting and defending liberal democracy in the U.S. and abroad. He serves as chairman of the group. Kasparov is also a security ambassador for the software company Avast.