Matthew James Welsh OAM (born 18 November 1976) is an Australian swimmer who is the former world champion in the backstroke and butterfly.

He took two golds in 50-meter butterfly and 50-meter backstroke, during one hour, at the World Championships in Shanghai 2006.

Welsh retired from professional swimming in March 2008 when he failed to secure a place in the team for the Beijing Olympics.

[citation needed] His first big break came in 1998 at the world swimming championships in Perth, Western Australia with a gold in the 4x100-metre medley relay.

At 31 and after 11 years on the Australian Swim Team, Welsh was unable to beat the younger generation at the trials and was not selected to compete at the 2008 Summer Olympics in Beijing.