Leonid Zakharovych Stein (Ukrainian: Леонід Захарович Штейн; November 12, 1934 – July 4, 1973) was a Soviet chess Grandmaster from Ukraine.

His play there was excellent, finishing in a tie for 6th–7th places, but he was denied the right to advance to the Candidates' Tournament, because of a FIDE rule then in force which limited the qualifiers from any one country to three (in this case USSR).

Stein took fifth place, sufficient for qualification for any non-Soviet player, with an outstanding total of 16½ / 23, but was blocked from advancement.

He had finished behind fellow Soviets Mikhail Tal, Vasily Smyslov, and Boris Spassky, who, along with Danish GM Bent Larsen, had all scored 17 points.

He did represent the USSR at the Tel Aviv Olympiad that year, 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.

Stein had already qualified for the 1973 Petropolis Interzonal, and was considered a potential favorite to win the entire Candidates' cycle He died of a heart attack at the age of 38 at the Rossiya Hotel in Moscow as he prepared to leave for the European chess championships in Bath, England.

He was considered to be a brilliant attacking genius, but nevertheless played very sound chess, being less willing than Tal to complicate with unforeseeable results.