Alexander Alexandrovich Alekhine, PhD (Russian: Алекса́ндр Алекса́ндрович Але́хин, pronounced [ɐlʲɪkˈsandr ɐlʲɪkˈsandrəvʲɪtɕ ɐˈlʲoxʲɪn]; October 31 [O.S. October 19] 1892 – March 24, 1946) was the fourth World Chess Champion. He is often considered one of thegreatest chess players ever.

By the age of twenty-two, he was already among the strongest chess players in the world. During the 1920s, he won most of the tournamentsin which he played. In 1927, he became the fourth World Chess Champion by defeating José Raúl Capablanca, widely considered invincible, in what would stand as the longest chess championship match held until 1985.

In the early 1930s, Alekhine dominated tournament play and won two top-class tournaments by large margins. He also played first board for France in five Chess Olympiads, winning individual prizes in each (four medals and a brilliancy prize). Alekhine offered Capablanca a rematch on the same demanding terms that Capablanca had set for him, and negotiations dragged on for years without making much progress. Meanwhile, Alekhine defended his title with ease against Bogoljubov in 1929 and 1934. He was defeated by Euwe in 1935, but regained his crown in the 1937 rematch. His tournament record, however, remained uneven, and rising young stars like Keres, Fine, andBotvinnik threatened his title. Negotiations for a title match with Keres or Botvinnik were halted by the outbreak of World War II in Europe in 1939. Negotiations with Botvinnik for a world title match were proceeding in 1946 when Alekhine died in Portugal, in unclear circumstances.

Alekhine is known for his fierce and imaginative attacking style, combined with great positional and endgame skill. Alekhine is highly regarded as a chess writer and theoretician, producing innovations in a wide range of chess openings, and giving his name to Alekhine's Defence and several other opening variations. He also composed some endgame studies.

Alekhine was born into a wealthy family in Moscow, Russia on October 31, 1892. His father Alexander Ivanovich Alekhine was a landowner and Privy Councilor to the conservative legislative Fourth Duma. His mother, Anisya Ivanovna Alekhina (born Prokhorova), was the daughter of a rich industrialist. Alekhine was first introduced to chess by his mother, and older brother, Alexei, and an older sister, Varvara (Barbara).

Alekhine's first known game was from a correspondence chess tournament that began on December 3, 1902, when he was ten years old. He participated in several correspondence tournaments, sponsored by the chess magazine Shakhmatnoe Obozrenie ("Chess Review"), in 1902–1911. In 1907, Alexander played his first over-the-board tournament, the Moscow chess club's Spring Tournament. Later that year, Alexander tied for 11th–13th in the club's Autumn Tournament; his older brother, Alexei, tied for 4th–6th place. In 1908, Alexander won the club's Spring Tournament, at the age of fifteen. In 1909, he won the All-Russian Amateur Tournament in Saint Petersburg. For the next few years, he played in increasingly stronger tournaments, some of them outside Russia. At first he had mixed results, but by the age of sixteen he had established himself as one of Russia's top players. He played first board in two friendly team matches: St. Petersburg Chess Club vs. Moscow Chess Club in 1911 and Moscow vs. St. Petersburg in 1912 (both drew with Eugene Znosko-Borovsky). By the end of 1911, Alekhine moved to St. Petersburg, where he entered the Imperial Law School for Nobles. By 1912, he was the strongest chess player in the St. Petersburg Chess Society. In March 1912, he won the St. Petersburg Chess Club Winter Tournament. In April 1912, he won the 1st Category Tournament of the St. Petersburg Chess Club. In January 1914, Alekhine won his first major Russian tournament, when he tied for first place with Aron Nimzowitsch in the All-Russian Masters Tournament at St. Petersburg. Afterwards, they drew in a mini-match for first prize (they both won a game). Alekhine also played several matches in this period, and his results showed the same pattern: mixed at first but later consistently good.

In April–May 1914, another major St. Petersburg 1914 chess tournament was held in the capital of the Russian Empire, in which Alekhine took third place behind Emanuel Lasker and José Raúl Capablanca. By some accounts, Tsar Nicholas II conferred the title of "Grandmaster of Chess" on each of the five finalists (Lasker, Capablanca, Alekhine, Tarrasch, and Marshall). Chess historian Edward Winter has questioned this, stating that the earliest known sources that support this story are an article by Robert Lewis Taylor in the June 15, 1940 issue of The New Yorker and Marshall's autobiography My 50 Years of Chess (1942). Alekhine's surprising success made him a serious contender for the World Chess Championship. Whether or not the title was formally awarded to him, "Thanks to this performance, Alekhine became a grandmaster in his own right and in the eyes of the audience." In July 1914, Alekhine tied for first with Marshall in Paris.

After World War II, Alekhine was not invited to chess tournaments outside the Iberian Peninsula, because of his alleged Nazi affiliation. His original invitation to the London 1946 tournament was withdrawn when the other competitors protested.

While planning for a World Championship match against Botvinnik, Alekhine died in his hotel room in Estoril, Portugal on March 24, 1946. The circumstances of his death are still a matter of debate. It is usually attributed to a heart attack, but a letter in Chess Life magazine from a witness to the autopsy stated that choking on meat was the actual cause of death. At autopsy, a three-inch long piece of unchewed meat was discovered blocking his windpipe. Some have speculated that he was murdered by a French "death squad". A few years later, Alekhine's son, Alexander Alekhine Junior, said that "the hand of Moscow reached his father". Canadian Grandmaster Kevin Spraggett, who has lived in Portugal since the late 1980s, and who has thoroughly investigated Alekhine's death, favors this possibility. Spraggett makes a case for the manipulation of the crime scene and the autopsy by the Portuguese secret police PIDE. He believes that Alekhine was murdered outside his hotel room, probably by the Soviets.

Alekhine's burial was sponsored by FIDE, and the remains were transferred to the Cimetière du Montparnasse, Paris, France in 1956.