Ian Thorpe, Australia's most successful Olympian, ended months of speculation by announcing his return to the pool with the intention of swimming at next year's London Games on Wednesday.
The 28-year-old, nicknamed "Thorpedo", quit competition in 2006 after a glittering career in which he captured nine Olympic medals -- five gold, three silver and a bronze -- at the 2000 and 2004 Games along with 11 world championship titles.
"I never thought I would be swimming in a competitive way again but I am glad that I am," said Thorpe.
"I have spent four years away from the pool and I needed those four years.
Thorpe said he had registered for the drug-testing regime on Wednesday as he was required to do nine months before beginning competition.
At the height of his career, Thorpe was the greatest middle distance freestyler of all time, he was never beaten in the 400 metres and only once over 200, but he said he would now target the relays and the 100 and 200 freestyle.
"I'm in the process of turning myself into a sprinter who can also maybe do a good 200 as well," he said.
Thorpe said he would, however, swim in an individual event in London if he qualified at Australia's Olympic trials in early 2012, but cautioned his compatriots to be realistic about what he could achieve.