American swimmer Caeleb Dressel set the new world record in the men’s 100 meter butterfly on Friday during the World Championships in Gwangju, South Korea.
Dressel came in at 49.50 during the second semi-final in the event, breaking the old record of 49.82 set by Michael Phelps in August 2009.
It's the second world record once held by Phelps to be broken this week.
Hungarian swimmer Kristof Milak broke Phelps' world record in the 200 meter butterfly on Wednesday while winning gold at the world championships.
Olympic gold medalist Missy Franklin also had a record broken, this one in the 200 meter backstroke by 17-year old Regan Smith.
Smith clocked in at 2:03.35, besting Franklin's old record of 2:04.06 set at the 2012 Summer Olympics in London.
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