Vyacheslav Vulfovich Osnos (24 July 1935 - 27 August 2009) was a Russian chess player, trainer and author. He was awarded the International Grandmaster title in 1965.

Osnos participated in the Soviet championship final six times from 1963 to 1968. In 1963, he won the semifinal ahead of Boris Spassky, Alexei Suetin, Igor Bondarevsky and Yuri Averbakh but finished last place of 20 in the final. In 1964, he finished second behind Viktor Korchnoi at the Leningrad Championship, which count double as a semi-final in the Soviet Championship. Finally, he got 10th place at the Soviet Championship and Korchnoi won the tournament. In 1965, he finished third in the semi-final then he achieved the best result of his career at the Soviet Championship: he finished 8th in the final behind Leonid Stein, but ahead of such players as David Bronstein or Viktor Korchnoi. In 1966, he tied for 14th place, in 1967, in the first Soviet Championship, which run under the Swiss system, he finished among the first 10. At the 1968/1969 Soviet Championship he tied for 11th.

In 1968, he tied for first place at the Leningrad championship but he lost the play-off against Valery Bykov and Alexander Cherepkov. In the following year, he won an international tournament in Debrecen. In 1970, he finished third place at the Leningrad championship and, finally, in 1971 and 1980 he won.

Between 1968 and 1974 he was one of Viktor Korchnoi’s coaches, in 1974 he was awarded with the title of Honoured Trainer of the Soviet Union. In 1974, he assisted Korchnoi at the Moscow World Championship Candidate’s Final against Anatoly Karpov.

Osnos co-authored with Peter Wells in writing The Complete Richter-Rauzer (The CompleteRichter-Rauzer 1988, Batsford).

His highest score was 2656 during his career according to Chessmetrics historical rating.

Sources: https://en.wikipedia.org; http://www.chessmetrics.com