Regan Dean Harrison (born 25 November 1977) is an Australian former breaststroke swimmer of the 1990s and 2000s, who won the silver medal at the 2000 Summer Olympics in Sydney as part of the 4×100-metre medley relay team.

The following year he finished second at the Australian Championships behind Ryan Mitchell, earning himself selection for the Sydney Olympics.

Harrison combined with Matt Welsh, Geoff Huegill and Michael Klim to claim silver, behind the United States who broke the world record.

He combined with Welsh, Huegill and Ian Thorpe to win gold in the 4×100-metre medley relay.

Harrison had a poor year in 2002, managing only seventh in the 200-metre breaststroke at the 2002 Commonwealth Games in Manchester, and being dropped for the 100-metre event and the medley relay.