H2O: Just Add Water, more commonly referred to as H2O, is an Australian fantasy children and teen drama television 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 are mermaids and each has their own unique, supernatural power related to water.

Only two series with a total of 52 episodes were originally planned, but due to popular demand, a third series was filmed. Series 1 premiered in July 2006, followed by series 2 in September 2007. Series 3 first aired in the United Kingdom in October 2009, with the Australian premiere occurring in May 2010.