Phelps held national swimming records by age 10 and became the youngest male Olympian since 1932 at age 15.
Even though he had just won four gold medals at the 1984 Olympics, he was dropped from Nike and Coca-endorsement Cola's programs.
Jesse Owens' four gold medals in the 1936 Olympics in Berlin had more meaning than any other athlete's.
Simone Biles won four gold medals at the 2016 Olympics, including all-around and floor exercise, and led the U.S. to team gold.
Mark Spitz won seven gold medals and set world records in every event at the 1972 Olympics. Michael Phelps broke that record at the 2008 Olympics.
Jackie Joyner-Kersee medaled in four successive Olympics, including gold in the heptathlon and long jump in 1988.
Michael Johnson was the only male athlete to win both the 400- and 200-meter dashes at the same Olympics.
Wilma Rudolph won a bronze medal in the 400-meter relay at the 1956 Olympics, a forerunner to her international stardom four years later.
Greg Louganis became the first man to sweep the diving events in successive Olympics.
Dara Torres won 12 gold medals despite missing the 1996 and 2000 Olympics and sitting out 2004 and 2008.