Supporters and rivals alike said the freestyle swimmer, who announced his retirement Tuesday, would be sadly missed from the competition pool. But no one begrudged him an end to the pre-dawn starts and the daily hours of chlorine-soaked training that have dominated his life for more than a decade.

Thorpe, 24, ended weeks of speculation about his future with the announcement he was giving up competitive swimming, taking himself out of the world championships in Melbourne next year and the Beijing Olympics in 2008.

``His retirement is an enormous loss to Australian swimming,'' Australian Prime Minister John Howard said.

His achievements _ which brought him five Olympic gold medals and 13 world records _ would be remembered by millions of Australians, said Howard.

``There have been so many great performances that they do all tend to merge into a recollection of a remarkable athlete, a great swimmer (and) a good bloke,'' Howard said. ``I wish him every success and happiness in the years ahead.''

Thorpe burst onto the swimming scene as a teenager and swam 13 long-course world records between 1999 and 2002, becoming an international star along the way with his own underwear label and sponsorship and endorsements worth millions from the likes of Omega and Adidas.

He has recently been plagued by illness, injury and a lack of motivation, and hasn't competed in a major international event since the Athens Olympics in 2004.

Thorpe's Australian teammate Grant Hackett, holder of the 1,500-metre world record and the Olympic champion over the distance, said it was a sad day for the sport.

``Not just for Australian swimming but for world swimming,'' Hackett said. ``They've lost one of their great athletes and a guy who has brought so much to the sport. Swimming's always been big at the Olympics and world championships, but he made it bigger than ever.''

``True hero of the pool has swum his last lap,'' said the front page headline of Sydney's The Daily Telegraph.

Thorpe and American Michael Phelps are acknowledged as the world stars of the sport.

Phelps said Thorpe was ``an inspiration and a terrific champion.''

``He elevated the worldwide interest in swimming and was a great ambassador to our sport,'' Phelps said in a statement. ``I wish him the best of luck in the future.''

Thorpe's retirement ends one of sport's great rivalries, U.S. Olympic Committee spokesman Darryl Seibel said.

``Ian Thorpe is a great Olympic champion and his accomplishments and contributions to the sport are legendary,'' Seibel said.

``Whenever Michael Phelps and Ian Thorpe were on the pool deck together, there was instant electricity,'' he said. ``You couldn't wait for the race to start and once it did, you didn't want it to end. It was captivating ... two great competitors who brought out the best in each other and represented the highest values of international competition.''

Australian great Dawn Fraser, who won the women's 100-metre freestyle at the 1956, 1960 and 1964 Olympics, said she had hoped Thorpe would continue on to Beijing and match or exceed her feat of gold at three consecutive Olympics.

``I guess in a way I'm sad, but that's selfish of me,'' Fraser said. ``He's made that decision for himself, he doesn't want to put himself under any more pressure.

``Ian, I thank you for what you've done for Australian swimming, go off now and enjoy your life and have a great time.''