Strengthening her lead almost the entire race, she headed into the 750-metre turn under world-record pace, and pulled off a stunning upset from the rest of the field to post a personal best and smash Janet Evans' 23-year-old U.S. record in 8:14.63.

[3] Meanwhile, Great Britain's Rebecca Adlington, the reigning Olympic champion, tried to hold on with Ledecky earlier through the race, but faded down the stretch to pick up a bronze in 8:20.32.

[4][5] New Zealand's Lauren Boyle produced a spectacular swim to finish with a fourth-place time and an Oceanian record in 8:22.72.

[6] Meanwhile, Denmark's Lotte Friis, the defending bronze medalist, opened up the race with an early lead, but dropped back to fifth in 8:23.86 to hold off a fast-charging Hungarian Boglárka Kapás (8:23.89) on the final lap by almost a fingertip.

France's Coralie Balmy (8:29.26) and Venezuela's Andreina Pinto (8:29.28) rounded out the field in one of the program's long-distance pool races.