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 holds the world record in the 50-metre backstroke (long course).
Born on 7 May 1985, his first experience of swimming was waiting poolside while his older brother was learning to swim at a swimming school. Tancock was competing in local swimming competitions by the age of nine. Tancock played for Exeter Chiefs rugby team as a winger until he was thirteen. His coach, Jon Randall, convinced him to choose swimming over rugby. He attended Loughborough College where he studied sports science and was awarded with a degree validated by Loughborough University.
As a junior for the Exeter Swimming Club, he competed at the British Winter Championship in 2000 at the age of 15. He broke four records and won more medals than any junior under the age of 16 had before him.
He followed this with a gold medal at the 2001 Youth Olympic Games.
Two golds in 2002 at the World Schools Championships.
He competed at a senior level for the first time in 2005 at the 2005 World Aquatic Championships, where he took the bronze medal in the 50m backstroke.
At the Japan International Open in August 2007, he won two gold medals. The first was in the 100m backstroke, which broke the European record time, and his second was in the 200m individual medley with a time of 1:59.19, which was only the second time he had finished with a time of under two minutes. It was a new British record, beating the previous record by a second and a half.
Tancock won several medals at the 2008 World Short Course Championships in Manchester, including a British, European and Commonwealth record time of 50:14 to take the gold medal in the 100m backstroke. The time was only 0.14 seconds off the world record set by American Ryan Lochte. He also won silver in the 50m backstroke and 200m medley.