Garry Kimovich Kasparov (born Garik Kimovich Weinstein, 13 April 1963) is a Russian chess grandmaster, former World Chess Champion, writer, and political activist and commentator.

From 1984 until his retirement in 2005, Kasparov was ranked world No. 1 for a record 255 months overall for his career. His peak rating of 2851, achieved in 1999, was the highest recorded until being surpassed by Magnus Carlsen in 2013. Kasparov also holds records for the most consecutive professional tournament victories and Chess Oscars .

Kasparov became the youngest ever undisputed World Chess Champion in 1985 at age 22 by defeating then-champion Anatoly Karpov. 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. In 1997 he became the first world champion to lose a match to a computer under standard time controls when he lost to the IBM supercomputer Deep Blue in a highly publicized match. He continued to hold the "Classical" World Chess Championship until his defeat by Vladimir Kramnik in 2000. Despite losing the title, he continued winning tournaments and was the world's highest-rated player when he retired from professional chess in 2005.

After retiring, he devoted his time to politics and writing. He formed the United Civil Front movement, and joined as 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 2013 that he had left Russia for the immediate future out of fear of prosecution. Since 2014, he holds Croatian citizenship and owns a house in Makarska.

Kasparov is currently chairman for the Human Rights Foundation and chairs its International Council. In 2017, he founded the Renew Democracy Initiative (RDI), an American political organization promoting and defending liberal democracy in the U.S. and abroad. He also serves as chairman of the group. Kasparov currently lives in New York City.

Kasparov was born Garik Kimovich Weinstein (Russian: Гарик Вайнштейн, Garik Kimovich Vainshtein) in Baku, Azerbaijan SSR (now Azerbaijan), Soviet Union. His father, Kim Moiseyevich Weinstein, was Jewish, and his mother, Klara Shagenovna Kasparova, was Armenian. Kasparov has described himself as a "self-appointed Christian", although "very indifferent" and identifies as Russian: "although I'm half-Armenian, half-Jewish, I consider myself Russian because Russian is my native tongue, and I grew up with Russian culture."

Kasparov began the serious study of chess after he came across a chess problem set up by his parents and proposed a solution. When Garry was seven years old, his father died of leukemia. At the age of twelve, Garry, upon request of his mother Klara and with the consent of the family, adopted Klara's surname Kasparov, which was done to avoid possible antisemitic tensions, which were common in the USSR at the time.

From age 7, Kasparov attended the Young Pioneer Palace in Baku and, at 10 began training at Mikhail Botvinnik's chess school under noted coach Vladimir Makogonov. Makogonov helped develop Kasparov's positional skills and taught him to play the Caro-Kann Defence and the Tartakower System of the Queen's Gambit Declined. Kasparov won the Soviet Junior Championship in Tbilisi in 1976, scoring 7 points of 9, at age 13. He repeated the feat the following year, winning with a score of 8.5 of 9. He was being trained by Alexander Shakarov during this time.

In 1978, Kasparov participated in the Sokolsky Memorial tournament in Minsk. He had been invited as an exception but took first place and became a chess master. Kasparov has repeatedly said that this event was a turning point in his life, and that it convinced him to choose chess as his career. "I will remember the Sokolsky Memorial as long as I live", he wrote. He has also said that after the victory, he thought he had a very good shot at the World Championship.

He first qualified for the Soviet Chess Championship at age 15 in 1978, the youngest ever player at that level. He won the 64-player Swiss system tournament at Daugavpils on tiebreak over Igor V. Ivanov to capture the sole qualifying place.

Kasparov rose quickly through the FIDE world rankings. Starting with an oversight by the Russian Chess Federation, he participated in a grandmaster tournament in Banja Luka, Bosnia and Herzegovina (then part of Yugoslavia), in 1979 while still unrated (he was a replacement for the Soviet defector Viktor Korchnoi, who was originally invited but withdrew due to the threat of a boycott from the Soviets). Kasparov won this high-class tournament, emerging with a provisional rating of 2595, enough to catapult him to the top group of chess players (at the time, number 15 in the world). The next year, 1980, he won the World Junior Chess Championship in Dortmund, West Germany. Later that year, he made his debut as second reserve for the Soviet Union at the Chess Olympiad at Valletta, Malta, and became a Grandmaster.

As a teenager, Kasparov tied for first place in the USSR Chess Championship in 1981–82. His first win in a superclass-level international tournament was scored at Bugojno, Yugoslavia in 1982. He earned a place in the 1982 Moscow Interzonal tournament, which he won, to qualify for the Candidates Tournament. At age 19, he was the youngest Candidate since Bobby Fischer, who was 15 when he qualified in 1958. At this stage, he was already the No. 2-rated player in the world, trailing only World Chess Champion Anatoly Karpov on the January 1983 list.

Kasparov's first (quarter-final) Candidates match was against Alexander Beliavsky, whom he defeated 6–3 (four wins, one loss). Politics threatened Kasparov's semi-final against Viktor Korchnoi, which was scheduled to be played in Pasadena, California. Korchnoi had defected from the Soviet Union in 1976, and was at that time the strongest active non-Soviet player. Various political maneuvers prevented Kasparov from playing Korchnoi, and Kasparov forfeited the match. This was resolved by Korchnoi allowing the match to be replayed in London, along with the previously scheduled match between Vasily Smyslov and Zoltán Ribli. The Kasparov-Korchnoi match was put together on short notice by Raymond Keene. Kasparov lost the first game but won the match 7–4 (four wins, one loss).

In January 1984, Kasparov became the No. 1 ranked player in the world, with a FIDE rating of 2710. He became the youngest ever world No. 1, a record that lasted 12 years until being broken by Vladimir Kramnik in January 1996; the record is currently held by Magnus Carlsen.

Later in 1984, he won the Candidates' final 8½–4½ (four wins, no losses) against the resurgent former world champion Vasily Smyslov, at Vilnius, thus qualifying to play Anatoly Karpov for the World Championship. That year he joined the Communist Party of the Soviet Union (CPSU), as a member of which he was elected to the Central Committee of Komsomol in 1987.

The World Chess Championship 1984 match between Anatoly Karpov and Garry Kasparov had many ups and downs, and a very controversial finish. Karpov started in very good form, and after nine games Kasparov was down 4–0 in a "first to six wins" match. Fellow players predicted he would be whitewashed 6–0 within 18 games.

In an unexpected turn of events, there followed a series of 17 successive draws, some relatively short, and others drawn in unsettled positions. Kasparov lost game 27 (5–0), then fought back with another series of draws until game 32 (5–1), earning his first-ever win against the World Champion. Another 14 successive draws followed, through game 46; the previous record length for a world title match had been 34 games, the match of José Raúl Capablanca vs. Alexander Alekhine in 1927.

Kasparov won games 47 and 48 to bring the scores to 5–3 in Karpov's favour. Then the match was ended without result by Florencio Campomanes, the President of the Fédération Internationale des Échecs (FIDE), and a new match was announced to start a few months later. The termination was controversial, as both players stated that they preferred the match to continue. Announcing his decision at a press conference, Campomanes cited the health of the players, which had been strained by the length of the match.

The match became the first, and so far only, world championship match to be abandoned without result. Kasparov's relations with Campomanes and FIDE were greatly strained, and the feud between them finally came to a head in 1993 with Kasparov's complete break-away from FIDE.