Viktor Korchnoi, Russian chess player (b. 1931)
Viktor Lvovich Korchnoi (Russian: Ви́ктор Льво́вич Корчно́й, IPA: [vʲiktər lʲvovʲɪtɕ kɐrtɕˈnoj]; 23 March 1931 – 6 June 2016) was a Soviet (before 1976) and Swiss (after 1980) chess grandmaster and writer. He is considered one of the strongest players never to have become World Chess Champion.Born in Leningrad, Soviet Union, Korchnoi defected to the Netherlands in 1976, and resided in Switzerland from 1978, becoming a Swiss citizen. Korchnoi played four matches, three of which were official, against GM Anatoly Karpov. In 1974, Korchnoi lost the Candidates final to Karpov. Karpov was declared World Champion in 1975 when GM Bobby Fischer declined to defend his title. Korchnoi then won two consecutive Candidates cycles to qualify for World Championship matches with Karpov in 1978 and 1981, but lost both. The two players also played a drawn training match of six games in 1971.

Korchnoi was a candidate for the World Championship on ten occasions (1962, 1968, 1971, 1974, 1977, 1980, 1983, 1985, 1988 and 1991). He was also four times a USSR chess champion, five times a member of Soviet teams that won the European championship, and six times a member of Soviet teams that won the Chess Olympiad. He played competitive chess until old age. At age 75, he won the 2006 World Senior Chess Championship and became the oldest person ever to be ranked among the world's top 100 players.