Clifford Charles Devlin Thorburn CM (born 16 January 1948) is a Canadian retired professional snooker player.

Nicknamed "The Grinder" because of his slow, determined style of play, he won the World Snooker Championship in 1980, defeating Alex Higgins 18–16 in the final.

At the 1983 tournament, Thorburn became the first player to make a maximum break in a World Championship match, achieving the feat in his second-round encounter with Terry Griffiths.

[4]: 104  He was abandoned by his mother, and after spending about two years in an orphanage during a custody dispute, was raised by his father and his paternal grandmother.

He spent time with Fred Davis and Rex Williams when they toured Canada in 1970, and afterwards became a resident professional at the House of Champions club in Toronto.

[11] Thorburn travelled to England in 1973, and on the day of his arrival, the reigning world snooker champion Alex Higgins offered to play him for £5 a frame.

In the 1974 World Snooker Championship he defeated Alex McDonald 8–3 in qualifying then lost 4–8 to Paddy Morgan in the first round.

He started the 1974–75 snooker season with a victory in the 1974 Canadian Open, knocking out Willie Thorne and Graham Miles to reach the final, where he won 8–6 against Taylor.

In the last session, Thorburn again narrowed the gap to one frame, but then Spencer won three in a row to achieve victory at 25–21.

[18] He retained his Canadian Open title in 1979, taking a 10–3 lead over Terry Griffiths before winning the match in the deciding frame, at 17–16.

[20] In advance of the 1980 World Championship, he practiced at a club near the Crucible that was owned by a friend, and gave up smoking and drinking alcohol for a week before the tournament.

In the evening, he played cards and drank alcohol with friends until 5:00 am, resuming the match the next day by winning the first five frames in succession.

[22] In the last session of the match, Thorburn extended his lead to 15–7 by the mid-session interval, then won 16–7 with a break of 114 in the 23rd frame,[23] becoming the first player to reach a second final at the Crucible.

[24] Writing in The Times, Sydney Friskin described the match to this point as a contrast of styles: "the shrewd cumulative processes of Thorburn against the explosive break-building of Higgins".

[24] The BBC's television coverage of the final had been interrupted by the broadcast of live footage of the Iranian Embassy Siege.

[36] Following a 4–10 loss to Jimmy White in the first round of the 1982 World Snooker Championship, Thorburn decided to return to Canada.

While he was completing the break, play stopped on the tournament's second table because his friend and fellow Canadian Bill Werbeniuk wanted to watch.

[41] During the semi-final, which finished at 12:45 am,[3] Thorburn learnt that his wife Barbara had suffered a miscarriage on the day of his maximum break.

From 2–2 after the first four frames, Davis won four in a row to leave Thorburn behind 2–6, extending this to 2–9 at the start of the second session, and 5–12 at the end of the first day.

Thorburn fluked a pot on the green ball in the deciding frame, to leave White requiring snookers to win.

[49] Thorburn experienced success in the Scottish Masters, an invitational event which opened the snooker season, in 1985 and 1986.

[13] He won the opening ranking event in the 1985–86 snooker calendar, the Matchroom Trophy, where he beat Jimmy White in the final 12–10, having trailed 0–7.

The Association's disciplinary committee had decided that Thorburn had brought the sport into disrepute, as a drug test that he took at the 1988 British Open showed that he had "minute traces of cocaine in his urine sample".

[54] At the 1995 Thailand Open, ranked 54th, he defeated three players from the top 16, including second-ranked Steve Davis, to reach the semi-finals.

[61] During the 2006 World Championship, he flew to Sheffield to unveil a life-size painting of the maximum break that he made at the tournament in 1983.

[63] At the age of 70, Thorburn won the 2018 Seniors Masters at the Crucible Theatre, defeating Jonathan Bagley 2–0 in the final.