Michael's most memorable moments

Here's a look at five of his most memorable moments:

GREAT HAUL OF CHINA: Phelps will forever be linked to his remarkable performance in Beijing, where he won eight gold medals (five individual, three relays) to break Mark Spitz's iconic Olympic record. Only 11 other athletes have won as many gold medals in their careers as Phelps won during that magical week in China. For good measure, he set or was part of seven world records. The only time he missed out might have been his most impressive triumph - rallying to beat Milorad Cavic by one-hundredth of a second in the 100m butterfly.

DOUBLING DOWN: Phelps became the first swimmer to set world records in two different events on the same day at the 2003 world championships in Barcelona. He took down the mark in the 100m butterfly during a semifinal heat and smashed his own record in the final of the 200m individual medley about an hour later.