2000 — Makes first Olympic appearance at Sydney Games, becoming youngest male swimmer on the U.S. team at age 15. Finishes fifth in his only event, the 200-meter butterfly.
2001 — Becomes the youngest male (15 years, 11 months) to set a world record when he breaks the mark in the 200 fly, and takes the mark even lower at the world championship in Fukuoka, Japan, for the first of 26 long-course world titles.
2003 — Won four events at the world championships in Barcelona and became the only swimmer in history to set world records in different events on the same day.
August 2004 — Comes up short in attempt to break Mark Spitz's record of seven gold medals, winning six golds and two bronzes at the Athens Olympics. Nevertheless, IOC president Jacques Rogge declares Phelps "the icon of the games."
November 2004 — Arrested for drunken-driving in Maryland at age 19. Pleads guilty to driving while impaired, pays fine and serves probation.
2007 — Joins Spitz as the only swimmer to win seven events at a major international swimming competition during the world championships in Melbourne, Australia. Phelps has a shot at eight victories, but the heavily favoured U.S. team is disqualified from the 4x100-medley relay in the preliminaries while Phelps is resting up for the final.
2008 — Surpasses Spitz's iconic Olympic record with eight gold medals at the Beijing Games, setting seven world records in what is dubbed "The Great Haul of China." Becomes a major international star, even doing a stint as host of "Saturday Night Live."
2009 — Suspended for three months by USA Swimming after photo emerges in a British tabloid of him inhaling from a pipe used to smoke marijuana. Phelps apologizes and accepts the penalty.
2011 — Wins four golds at world championships in Shanghai, but is beaten by fellow American Ryan Lochte in their two head-to-head meetings. Lochte is the big star of the meet with five golds.
2012 — Claims four gold medals and two silvers at the London Olympics, which he says will be his final swim meet. Phelps retires with myriad Olympic records, including twice as many golds as anyone else (18) and 22 medals overall, four more than anyone else in any sport.