Tigran Vartanovich Petrosian was a Soviet Armenian Grandmaster, and World Chess Champion from 1963 to 1969. He was nicknamed "Iron Tigran" due to his almost impenetrable defensive playing style, which emphasized safety above all else. Petrosian is credited with popularizing chess in Armenia.
Petrosian was a Candidate for the World Chess Championship on eight occasions. He won the World Championship in 1963, successfully defended it in 1966, and lost it to Spassky in 1969. Thus he was the defending World Champion or a World Championship Candidate in ten consecutive three-year cycles. He won the Soviet Championship four times.