Australian swimmer Ariarne Titmus broke the women’s 400m freestyle world record — and defeated American rival Katie Ledecky and previous world record-holder Summer McIntosh of Canada — at the 2023 World Swimming Championships in Fukuoka, Japan, on Sunday.

Titmus, the reigning Olympic gold medalist in the event, led from 100 meters and ultimately clocked 3:55.38, cutting seven-hundredths off McIntosh’s world record and touching the wall more than three seconds ahead of Ledecky (3:58.73). New Zealand’s Erika Fairweather claimed bronze, while the 16-year-old McIntosh placed fourth.

Titmus, Ledecky, and McIntosh are the three fastest women to ever swim the 400m free and the event was billed as the ‘Race of the Century’ heading into this week’s world championships.

Ledecky owned the world record in the event from 2014 until last year, when Titmus claimed it for herself at Australian Championships. McIntosh then took it over at Canadian Trials in March.

“It wasn’t something (breaking the record) that I had my mind on for this meet,” Titmus told reporters in Japan. “I just wanted to come here and try and swim the way I know I’m capable of. I knew the only way to win — I believed — was to try to take it out (fast) and whoever had as much fight left at the end was going to win it.”

By taking silver, Ledecky claimed the 23rd world championship medal of her career, extending her mark as the most decorated female swimmer in world championship history.

“I think you could just see the world record coming. It’s been a very fast year of swimming and it was kind of predictable that it would be a really fast field,” Ledecky said. “I can’t really complain. My stroke feels good. I feel good in the water. I think all year my 800 has felt better than my 400, so I’m excited about the rest of my week.”

Round One of Ariarne Titmus versus Katie Ledecky goes to Ariarne Titmus.

Titmus took home gold in the 400-meter freestyle with a time of 3:56.69, setting an Australian record and falling just short of Ledecky’s world record from the 2016 Olympics. Ledecky came in second at 3:57.36, her fastest time since setting the world record in Rio.

The swimmers’ times were the second and third fastest in history. Titmus became the first swimmer to defeat Ledecky in an individual Olympic event.

The win spurred an immediately iconic reaction by Titmus’ coach Dean Boxall, who began coaching Titmus five years ago. Back then, Titmus was 16 seconds off of Ledecky’s world-record time.

Ledecky and Titmus return to action in the semifinals of the 200m freestyle on Monday at 9:30 p.m. ET on NBC. Ledecky, whose Olympic performance in 2016 (four golds, one silver) was the most decorated by a U.S. female athlete, won her heat of the 200m qualifiers Sunday night with a time of 1:55.28.

Ariarne Titmus might be excited about winning the 400m free gold at the Olympics.

But her coach Dean Boxall might be even more excited for her.

Boxall went viral for his reaction to Titmus winning gold over Katie Ledecky, scaring the usher behind him and creating one of those instantly iconic moments that the Olympics are known for.

But perhaps nothing is more iconic than Titmus’ race itself, as the 20-year-old fought back to overtake Ledecky in the final 100 and take home the gold.