Olympics 2012: Did Michael Phelps and Missy Franklin win more gold?
Phelps' 51.21-second victory in the 100-meter butterfly marked his record 17th gold and 21st medal overall in the Olympics.
This was Phelps' last individual race in his swimming career, which he'll cap off with Saturday's 4x100 medley relay.
Chad le Clos (South Africa) and Evgeny Korotyshkin (Russia) tied for silver with a finish time of 51.44.
Meanwhile, Franklin set a world record with her 200-meter backstroke victory, earning her third gold and fourth medal overall.
Her finish time of 2 minutes, 4.06 seconds, was the seventh world record set in the 2012 games.
Anastasia Zueva (Russia) took silver with a finish time of 2:05.92, and Franklin's USA teammate Elizabeth Beisel earned a bronze medal with a time of 2:06.55.