John Spencer (18 September 1935 – 11 July 2006) was an English professional snooker player who won the World Snooker Championship title at his first attempt in 1969, the year that the event reverted to a knockout tournament. He won the world title for the second time in 1971, and was the first player to win the championship at the Crucible Theatre when it moved there in 1977. Spencer was the inaugural winner of both the Masters and the Irish Masters tournaments, and was the first player to make a maximum 147 break in competition, although this is not recognised as an official maximum because the pockets on the table did not meet the required specifications.