Rob Schumacher, USA TODAY Sports
Phelps prepares to compete in the men's 200m butterfly semifinals during the London Olympics on Tuesday.
LONDON - Michael Phelps' last individual race of his Olympic career ended with another gold medal.
How could it not?
Arguably the greatest Olympian in history, he won his 21st overall medal by taking the 100-meter butterfly in 51.21 Friday night in the London Games. Chad le Close of South Africa and Evgeny Korotyshkin of Russis tied for silver.
He won the race on the second leg, falling behind at the start and standing seventh at the halfway point.
Phelps became the first man in Olympic history to win an individual swimming event at three successive Games in Thursday's 200 individual medley - and Friday's 100 butterfly allowed him to do that on successive nights. Phelps won the 100 fly in Athens in 2004 and Beijing in 2008.
Phelps came into the event with a career total of 20 Olympic medals, 16 of them gold, both records. He can add one last medal Saturday in the Olympic swim meet's final event, the men's 4x100 medley relay. Phelps, 27, said he will retire after the Games.
South Africa's Chad le Clos, who beat Phelps in the 200 butterfly, and Serbia's Milorad Cavic, who won silver behind Phelps in Beijing, entered the race as top contenders.
Two women have won individual swimming in three consecutive Games: Australia's Dawn Fraser (1956, 1960 and 1964) and Hungary's Krisztina Egerszegi (1988, 1992 and 1996).
Four years ago, Phelps set the world record in the Beijing Games in 50.58.