World record holder Leon Marchand claimed the 400 metres individual medley gold medal at his home Paris Olympics on Sunday to send fans into delirium at La Defense Arena.
The 22-year-old, nicknamed the "French Michael Phelps", carried the expectations of a nation into his first event but he simply crushed his rivals in a swim of four minutes and 2.95 seconds that broke the Olympic record and flirted with his own World record mark.
It was not so much a contest as a coronation for Marchand, with Japan's silver medallist Tomoyuki Matsushita more than six seconds adrift. American Carson Foster took the bronze.
Prepared by Bob Bowman, the coach who turned American Phelps into a gold medal machine, Marchand will bid for another three individual events as the face of his home Games.
Phelps, working with U.S. broadcaster NBC at the Games, watched on at the stadium as his would-be successor was feted by the home fans.
The terraces were festooned with tricolore flags, and the fans generated a deafening roar as Marchand sped to the wall in the final freestyle leg.
Martinenghi ends Peaty's 'three-peat' dream
Italy's Nicolo Martinenghi won the men's 100 metres breaststroke gold and ended Adam Peaty's "three-peat" bid to win the same event at three successive Games.
Peaty, hoping to become only the second male swimmer after retired US great Michael Phelps to perform the triple, had to settle for silver alongside reigning world champion Nic Fink of the United States.
Both touched out in 59.05, just 0.02 of a second slower than Martinenghi's relatively sedate time.
The Italian told RAI television he had closed his eyes and hoped for the best.
"I showed that the time doesn't matter, it matters how you are, seizing the moment," he said.
Peaty had swam 58.86 on Saturday, some way off the 57.94 he produced at the British championships in April. He holds the world record of 56.88 set in Gwangju, South Korea, in 2019 plus the Olympic record of 57.13 from Rio 2016.
"I gave it my absolute all," Peaty told the BBC. "I executed it as well as I could. It's not about the end goal, it's about the process.
Peaty started in lane four after powering into the final with the fastest time on Saturday, but he was second at the turn and it came down to a matter of milliseconds and a stroke or a glide at the finish.
"It doesn't matter what time it says on the scoreboard. I think in my heart I have already won. I'm so happy that I can race against the best in the world and still come joint-second," he said.