H2O: Just Add Water, also known as H2O, is an Australian fantasy children and teen drama TV show created by Jonathan M. Shiff. It first screened on Australia's Network Ten and as of 2009 ran in syndication in over 120 countries with a worldwide audience of more than 250 million. It was filmed on location at Sea World and other locations on the Gold Coast, Queensland, Australia. The show revolves around three teenage girls facing everyday teen problems with an added twist: they become mermaids with unique, supernatural powers over water.

Only two series with a total of 52 episodes were originally planned, but due to popular demand, a third series was filmed. Series one premiered in July 2006, followed by series two in September 2007. Series three first aired in the United Kingdom in October 2009, with the Australian premiere occurring in May 2010.