It's also the fifth-fastest time ever by Ledecky herself – who now owns the six fastest swims in the event.
Ledecky hadn't raced a 1 500m free – which is not an Olympic event for women – since setting the world record of 15:25.48 at the 2015 World Championships in Kazan, Russia.
"I wanted to try to put together a good swim. I was maybe a little aggressive on the first 50, but I was able to settle into a pretty good rhythm and pick it up the last 100m," said the American, who was nearly 40 seconds clear of the field.
