There's just no contest: Michael Phelps is the greatest Olympian of all time. He's racked up 28 medals (23 of them gold) and shattered world records. He's gone into retirement and come back out.

“Michael Phelps ... During the 2008 Olympics in Beijing, Phelps, who retired from competitive swimming in 2016, won eight gold medals. In addition to his 23 Olympic gold medals, he also has ...