Phoebe Jane Elizabeth Tonkin (born 12 July 1989) is an Australian actress and model. She is best known for portraying Cleo Sertori in H2O: Just Add Water, Fiona Maxwell in Tomorrow, When the War Began and Faye Chamberlain in The Secret Circle.

Tonkin's first television appearance was on the Australian teen show H2O: Just Add Water, where she played one of the main characters, Cleo Sertori. While not a strong swimmer, she worked to improve her abilities during pre-production of the show. On 20 October 2007, Tonkin appeared on the Nickelodeon UK Kids' Choice Awards, where she presented the award for best band alongside H2O co-stars Claire Holt and Cariba Heine.