Michael Phelps' performances at the 2004 and 2008 Olympics have brought him strong consideration as the greatest ever Olympian. He has surpassed the records of Mark Spitz and Johnny Weissmuller and is considered the greatest swimmer ever. Phelps swims several strokes, including butterfly and freestyle, but his best events are the individual medleys. At the 2004 Olympic Games, Michael Phelps became only the second athlete, after Aleksandr Dityatin (URS-GYM-1980) to win eight medals at a single Olympics, and he repeated this in 2008 at Beijing. Phelps had attempted to win gold medals in eight swimming events in 2004, to better... Mark Spitz's performance at München. Phelps did not manage that but did win six gold medals (four individual) and two bronze medals. He followed this with a dominating performance at the 2005 World Championships at which he won five gold medals and a silver medal. He had also won five World Championship gold medals at the 2003 meet.

Phelps not only did not stop competing but pushed his records even further. At the 2007 World Championships he entered eight events and won seven gold medals, losing out on the eighth in the 4×100 medley relay, when the USA was disqualified in an early round heat in which he had sat out. He seemed poised to challenge Spitz's 1972 mark of seven gold medals. At Beijing Phelps again entered eight events and this time he came thru with a victory in all eight, becoming the first Olympian to win eight gold medals at one Olympic Games.

After Beijing, Phelps took some time off and did not train as hard for a time, but he still won five gold medals and six medals at the 2009 World Championships. He won another five golds at the 2010 Pan-Pacs, and in 2011, won four gold medals and seven medals at the Worlds, setting him up for the 2012 Olympics, and giving him a total of 33 medals and 26 gold medals at the World Championships.

At London in 2012, Phelps cemented his title as the world's greatest swimmer and, to many people, as the world's greatest Olympian. He won four more gold medals and six medals, but actually failed to medal in one event in 2012, placing fourth in the 400 IM. His six medals in 2012 left him with absolute Olympic records of 22 medals and 18 gold medals. Phelps then announced his retirement, although in 2013 he has hedged that a bit, and suggested he may return to the pool for further competition.