Emotions ran high at the Paris La Defense Arena on Sunday as local hero Leon Marchand clinched France's first Olympic swimming gold medal since the London 2012 Games.

Willed on by frenzied support from home fans, Marchand led the men's 400m individual medley relay final at every turn to finish ahead of Japan's Tomoyuki Matsushita and Carson Foster of the United States in an Olympic record time of four minutes, 2.95 seconds.

Leon Marchand of France competes during the men's 400m individual medley final of swimming at the Paris 2024 Olympic Games in Paris, France, July 28, 2024. (Xinhua/Xia Yifang)

"I definitely dreamed of that before, every one of us did. Doing this in my hometown is pretty cool," Marchand said.

"The atmosphere was amazing, I don't know how to explain it. I had goosebumps before, and during the race too. On the breaststroke section I could hear everyone just cheering for me. That was special and winning today was really amazing for me."

Marchand entered the race with lofty expectations having set a new world record in the event last year, smashing Michael Phelps' previous mark that had stood for 15 years.

The 22-year-old appeared on track to break the record again on Sunday before fading slightly in the final 50m.

"The freestyle was a little tough at the end, but 4:02 is amazing, so I'm really amazed by today."

The packed arena was still buzzing from Marchand's performance when Torri Huske upstaged United States teammate and world record holder Gretchen Walsh to win a thrilling women's 100m butterfly final.

Huske secured the United States' second swimming gold medal of the Games by touching the wall in 55.59 seconds, just four hundredths of a second ahead of Walsh. China's Yufei Zhang, a silver medalist in this event at the Tokyo 2020 Games, took bronze in 56.21.

For Huske, it represented redemption after she missed out on a medal in this event at the Tokyo Olympics by one hundredth of a second.

After an unremarkable start, the 21-year-old powered home in the last 50m as Walsh appeared to tire.

"Last time I just missed the podium and I'm not going to lie, that was devastating," Huske said.

Walsh, who set a world record in the event at the US Olympic trials in June and broke the Olympic record in Saturday's semifinal, said she had hoped for better.

"It wasn't exactly the time I was looking for, I feel like I am capable of more," she said.

In the night's only other medal race, Italy's Nicolo Martinenghi produced a storming finish to win the men's 100m breaststroke gold in dramatic fashion.

The 24-year-old finished in 59.03 seconds, just two hundredths of a second ahead of Britain's Adam Peaty, who was aiming to become only the second swimmer after Phelps to win gold in the same event at three Games.

Nic Fink of the United States took bronze, less than a hundredth of a second behind Peaty.

"It's a dream come true," Martinenghi said. "I dreamed of this when I was young, so I grow with this as a goal in my mentality, I prepare, I build my wall.

"Today's the final step, the gold medal in the Olympic Games, that's my dream. I don't know what to say. I can say that I am Olympic champion."