Ian James Thorpe OAM (born 13 October 1982 in Sydney, New South Wales), also known as the Thorpedo or Thorpey, is a former Australian freestyle swimmer. He has won five Olympic gold medals, the most won by any Australian, and in 2001 he became the first person to win six gold medals in one World Championship. In total, Thorpe has won eleven World Championship golds, the second-highest number of any swimmer. Thorpe was the first person to have been named World Swimmer of the Year four times by Swimming World Magazine, Hunter (2004), p viii and was the Australian swimmer of the year from 1999 to 2003. His athletic achievements made him one of Australia's most popular athletes, with his philanthropy and clean image earning him further recognition as the Young Australian of the Year in 2000.

At the age of 14, he became the youngest male ever to represent Australia, and his victory in the 400 metre freestyle at the 1998 Perth World Championships made him the youngest ever individual male World Champion. pp. 434–436. After that victory, Thorpe dominated the 400 m freestyle, winning the event at every Olympic, World, Commonwealth and Pan Pacific Swimming Championships until his break after the 2004 Olympics. Aside from 13 individual long-course world records, Thorpe anchored the Australian relay teams, numbering the victories in the 4 × 100 m and the 4 × 200 m freestyle relays in Sydney, among his five relay world records. His wins in the 200 m and 400 m and his bronze in the 100 m freestyle in Athens have made him the only person to have won medals in the 100-200-400 combination.

After the Athens Olympics, Thorpe took a year away from swimming, scheduling a return for the 2006 Commonwealth Games. However, he was forced to withdraw due to illness. Subsequent training camps were interrupted, and he announced his retirement in November 2006, citing waning motivation.