Watch Michael Phelps wins 21st Olympic gold medal at Rio

Catch Michael Phelps wins 21st Olympic gold medal. Michael Phelps wins 21st Olympic gold medal as U.S. dominates 4x200-meter freestyle relay.

#USABasketball cheering on Phelps. https://t.co/EFxi4YuP5o

— Finish Line (@FinishLine) August 10, 2016