Leonid Zakharovich Stein was born in (the) Ukraine. He became a master at the age of twenty-four--unusually late for one who goes on to become a player of his caliber. Three years later, Stein qualified for the Soviet Championship for the first time, placing third and gaining the International Grandmaster title (1962). He played board one for the Soviet team at the Helsinki 1961 Student Olympiad, scoring a strong +8, =3, -1, and helping his team to the overall gold medals. He also represented the USSR at the Tel Aviv Olympiad (1964) scoring a fine 10/13, and winning an individual gold medal on the first reserve board. Again, he was in the Soviet side at the Havana Olympiad 1966, scoring 9/12, winning an individual silver medal on board four. Both times, the Soviet Union won the team gold medals. In the 1960s, he accumulated a string of strong tournament victories, including three U.S.S.R. Championships 1963 [rusbase-1], 1965 [rusbase-2] and 1966/7 [rusbase-3]. Although Stein never qualified for the Candidates, he came extremely close in 1962 and 1964 (when he would have qualified if not for a rule restricting the number of candidates from one country) and again in 1967 (where he was eliminated after drawing a tie-break playoff with Vlastimil Hort and Samuel Reshevsky due to the latter's better tiebreaks).
Two outstanding international tournament victories were attained at Moscow 1967 (commemorating the 50th anniversary of the 1917 October Revolution), and Moscow 1971 (Alekhine Memorial, equal with Anatoly Karpov). Both of the Moscow tournaments were considered to be among the strongest tournaments in chess history up to that time. Further international tournament victories were scored at Sarajevo (Bosna) 1967, equal with Borislav Ivkov, Hastings 1967/68 shared, Kecskemet 1968, Tallinn 1969, Parnu 1971, and Las Palmas 1973, equal with Tigran Petrosian.
As Stein was preparing to leave for Bath, England (1973) for the European Team Championship, he collapsed and died of an apparent heart attack in the Rossiya Hotel in Moscow, aged 38.
Stein defeated many of the top players of his era. He was one of the few players who had an even score against Vasily Smyslov, Tigran Petrosian, and Mikhail Botvinnik. He had plus records against Mikhail Tal, Boris Spassky, and Paul Keres.
Garry Kasparov wrote that Stein "went beyond the bounds of Botvinnik-Smyslov harmony, expanding the limits of our understanding of the game, changing our impressions of the correlation of material and quality of position, of situations with disrupted material and strategic balance, and created the grounds for the emergence of modern, ultra-dynamic chess". (My Great Predecessors Vol. 3, p. 231)
Wikipedia article: Leonid Stein