Liam John Tancock (born 7 May 1985) is an English former competitive swimmer who represented Great Britain in the Olympics, FINA world championships, and European championships, and England in the Commonwealth Games. He specialised in backstroke and individual medley events. He is a three-time world champion and a four-time Commonwealth Games gold medallist, and held the world record in the 50-metre backstroke (long course) for almost a decade.