Thorpe's announcement, which was covered live by several television networks and led news bulletins around Australia, came after he said he had realised there was more to life than swimming.

Known as "Thorpedo", he lifted his sport's profile and constantly raised the bar through his sublime swimming technique and striking physique, which earned him astonishing success.

He stands in the pantheon as one of the greatest swimmers in Olympic history, winning five gold medals over two Games, the most by an Australian, 11 world titles and 13 individual world records.

Thorpe's retirement was met with expressions of regret and admiration from Australia's political and sporting leaders.

Prime Minister John Howard called him "a remarkable athlete, a great swimmer, a good bloke".

Australian Olympic Committee president John Coates led the accolades, saying Thorpe's legacy would be long-lasting.