Efim Petrovich Geller (, ; 8 March 1925 – 17 November 1998) was a Soviet and Russian chess player and world-class grandmaster at his peak. He won the Soviet Championship twice (in 1955 and 1979) and was a Candidate for the World Championship on six occasions (1953, 1956, 1962, 1965, 1968, and 1971). He won four Ukrainian SSR Championship titles (in 1950, 1957, 1958, and 1959) and shared first in the 1991 World Seniors' Championship, winning the title outright in 1992.