Clifford Charles Devlin (Cliff) Thorburn (born January 16, 1948 in Victoria, British Columbia, Canada) is a retired professional snooker player. His slow, determined style of play earned him the nickname The Grinder.
Thorburn's finest moment came in the 1980 World Championship. He met Alex Higgins in the final, two personalities that could hardly be more different. Thorburn won the match 18-16 to take the championship, and rose to number two in the world rankings. The BBC's coverage of the final had been interrupted by the broadcast of live footage of the SAS storming the Iranian Embassy. The following season Thorburn reached the number one spot. In 1977 and 1983 he lost in the World final to John Spencer and Steve Davis respectively. In the latter final his wife had miscarried shortly before the match which may partly explain his very heavy defeat by Davis.
In 1983, Thorburn became the first player to make a maximum 147 break at the World Championships. The achievement took place in a match against Terry Griffiths, and was made more notable by the fact that it stopped the match going on at the tournament's second table: Thorburn's friend and fellow Canadian Bill Werbeniuk wanted to watch the break instead of playing his own match; and joined in the celebrations with Thorburn and Griffiths when the break was completed. That same year, he was made a Member of the Order of Canada. During the 2006 World Championships, Thorburn flew to Sheffield to unveil a lifesize painting of his break, by the artist Michael Myers. It is on display at the Macdonald St. Paul's Hotel in Sheffield. 
Thorburn was fined by World Snooker for using cocaine in 1989 and retired from professional snooker in 1996, but still plays the game. He enters competitions held in Canada.
He is the father of two boys, Jamie and Andrew.