Katie Ledecky has set an Olympic record with the fastest time in the 800-meter freestyle preliminaries.

The 19-year-old American swam the 16-lap event in 8 minutes, 12.86 seconds Thursday, bettering the old mark of 8:14.10 set by Rebecca Adlington of Britain in 2008.

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Ledecky's time was nearly seven seconds faster than anyone else.

She will swim the final Friday night, seeking to complete a sweep of the 200, 400 and 800 freestyles for the first time since the 1968 Mexico City Games. 

Ledecky also crushed her world record in the 400m freestyle.

The American phenom surged home to touch the wall in 3:56.46, smashing her own world record of 3:58.37 set in the Gold Coast, Queensland in 2014.

Ledecky, who has gone from strength to strength since her surprise win in the 800m free as a 15-year-old in London, has now broken 12 world records since then. 

On Wednesday, she continued her winning streak, giving Team USA their only gold medal win in what was an unusually disappointing performance in the pool that night.

Ledecky anchored the women and crushed Australia’s lead in the 4x100m freestyle relay, helping the US win its second-straight Olympic gold in the event.

It was the first gold medal in Rio for Ledecky’s teammates Maya Dirado, Leah Smith and Allison Schmitt.

Ledecky has already won gold in the Women’s 200m freestyle and 400m freestyle, as well as a silver in the Women’s 4x100m freestyle relay.

The sensational swimmer will have one more chance to win gold in Rio with the Women's 800m freestyle.