Katie Ledecky is the fastest woman in the world in the pool. The American beat her own world record in the 400-meter freestyle on Sunday night by turning in a time of 3:56.46, beating her own record by two seconds and a clear five seconds ahead of her next closest competitor.

"I was really confident. The 3:58 this morning felt really easy," Ledecky said. "I knew if could just push the back half really hard, I could make it happen tonight. The goal was 3:56 so I'm really happy. Check that one off."

Ledecky was a woman among girls on Sunday. After the first 50 meters, no competitor even came close to her side in the race. Just look at this distance.

It is Ledecky's first gold of these games and she will have three more chances later on this week in the 200-meter freestyle, 800-meter freestyle and 4x200-meter freestyle relay.