(CNN) — Although Michael Phelps retired seven years ago, his legacy has continued to tower over swimming.

But on Saturday, Phelps’ last remaining world record was smashed by 21-year-old Leon Marchand at the World Aquatics Championships in Fukoka, Japan, as the Frenchman completed the 400 meters individual medley in 4:02.50, shaving an enormous 1.34 seconds off Phelps’ previous mark.

“That was insane, one of the most painful things I’ve done. It was amazing to do it here and the time is crazy,” Marchand said afterwards, according to the Olympics’ official website, “The best is yet to come.”

Marchand was just six years old when Phelps set the previous world record in the discipline, at the 2008 Beijing Olympics, and he was presented with the gold medal afterwards by the legendary American swimmer.

Phelps himself had held the world record for almost 21 years, setting a series of increasingly faster times during his stint as the world’s most dominant swimmer.

“It’s excellent, I train everyday for that,” Marchand added. “I’m two seconds faster than my previous record, I beat the world record, it’s amazing… I don’t know what to say, I’m so happy.”

The 21-year-old was under Phelps’ world record pace for the entirety of his swim, eventually finishing more than four seconds ahead of the USA’s Carson Foster in second and almost seven seconds ahead of Japan’s Seto Daiya in third, as he secured his third ever gold medal at the world championships.

Meanwhile Australia’s Ariarne Titmus set a world record in the women’s 400 meter freestyle with a time of 3:55.38, so blistering that she held off Katie Ledecky in second place.

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