Olympic Swimming Great -- HOSPITALIZED IN AUSTRALIA ... Won't Compete Again, Agent Says

Olympic swimming legend Ian Thorpe -- who won FIVE gold medals for Australia over the years -- has been hospitalized in Sydney after suffering a serious infection in his shoulder ... and his agent says he will never swim competitively again.

The 31-year-old's agent told local media, "He’s contracted two forms of bugs in hospital. He’s undergone two or three operations over the last two months so ... I mean bad luck. He’s quite sick but that’s the situation."

"It’s serious but it’s not life-threatening," he said.

Thorpe's agent says reports that he will lose his arm are untrue -- but does say, "From a competitive point of view -- he will not be swimming competitively again I don’t think."

Thorpe is a legend in Australia -- winning a total of 9 Olympic medals from the 2000 and 2004 games.