Lembit Oll (23 April 1966 in Kohtla-Järve - 17 May 1999 in Tallinn) was an Estonian chess grandmaster. He was already successful as a junior, becoming champion of Estonia in 1982 and junior champion of the Soviet Union in 1984. He also won multiple European and World junior championships. FIDE awarded him the IM title in 1983 and the GM title in 1990. From that moment, he regularly played for Estonia during Chess Olympiads and European team championships. Early 1998 he reached his highest position on the FIDE ranking list: 2655. He played his last tournament in 1999 in Nova Gorica reaching a shared second position.
Oll, who was married with two sons, fell into severe depression after he divorced. He committed suicide by jumping out of the window of his house on the fifth floor. Despite his personal problems, he still held the 42nd place on the world ranking list at that time. He was buried at Metsakalmistu cemetery in Tallinn, not too far away from the most famous Estonian chess player Paul Keres.
Oll played for Estonia four times in Chess Olympiads.