Giaan Leigh Rooney, OAM[4] (born 15 November 1982)[5] is an Australian former competitive swimmer and television personality.

[10] Rooney made her international swimming debut for Australia at the 1998 Commonwealth Games, where she won a gold medal in the 100 m backstroke as a 15-year-old.

[14] This meet was also widely remembered for the disqualification of the Australian women's team after they jumped in the water to celebrate apparent victory in the 4×200-metre freestyle relay: the team of Elka Graham, Petria Thomas and Linda Mackenzie joined anchor swimmer Rooney in the water to celebrate their win, but as it was before all other competitors had finished the event, they were disqualified.

[15][16] Rooney competed in the 2002 Commonwealth Games in Manchester, England, winning silver in the 4×200-metre freestyle relay (with Elka Graham, Rebecca Creedy and Petria Thomas) and bronze in the 100-metre backstroke.

[17] In 2004 Rooney won a gold medal in world record time at the 2004 Summer Olympics in the women's 4×100-metre Medley Relay.

After the withdrawal of Grant Hackett from the 2006 Commonwealth Games due to injury, Rooney was appointed as the captain of the national swimming team.

[7] Rooney has performed on television with appearances on Torvill and Dean's Dancing on Ice competition and holiday season weather presenter on Nine Network's Today, filling in for Steven Jacobs, despite having no experience or qualification in meteorology.