Garry Kimovich Kasparov (Russian: Гарри Кимович Каспаров, Russian pronunciation: [ˈɡarʲɪ ˈkʲiməvʲɪtɕ kɐˈsparəf], born Garik Kimovich Weinstein, Гарик Кимович Вайнштейн; 13 April 1963) is a Russian chess grandmaster, former World Chess Champion, writer, political activist and commentator. His peak rating of 2851, achieved in 1999, was the highest recorded until being surpassed by Magnus Carlsen in 2013. From 1984 until his retirement in 2005, Kasparov was ranked world No. 1 for a record 255 months overall for his career, which outstrips all other previous and current chess ranking records. Kasparov also holds records for the most consecutive professional tournament victories (15) and Chess Oscars (11).

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.

Since retiring, he has 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 persecution. Following his flight from Russia, he had 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 currently chairman of 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 serves as chairman of the group. Kasparov is also a Security Ambassador for the software company Avast.