Hungary's Kristof Milak won the men's 100m butterfly in 50.33 seconds at the European Championships in Rome on Sunday.
The 22-year-old Olympic silver medallist pipped Switzerland's Noe Ponti in second place with Poland's Jakub Majerski in third.
Milak was in line to beat his own continental record of 49.68sec at the halfway stage before slowing down in the final 50m in the open-air pool at the Foro Italico complex.
Elsewhere, France's Analia Pigree claimed the women's 50m backstroke in 27.27sec, almost 0.30sec slower than the world record with Italy's Silvia Scalia in second and the Netherlands' Maaike de Waard taking bronze.
"I'm absolutely happy, I'm in shock," 21-year-old Pigree said.
"It's my first long-course championships and my first medal, and this gives me strong motivation to carry on," she added.
Later, Britain's James Wilby claimed gold in the men's 200m breaststroke after starting in lane No 8 in 2min 08.96s with Finland's Matti Mattson in second and home favourite Luca Pizzini in third.
Wilby, 28, also raced in the world championships earlier this summer and in the Commonwealth Games with the competitions having been re-scheduled due to the Covid-19 pandemic.
"It was a real wrestle in that last 25 but I executed my process just how I wanted to," Wilby said.
"It's extremely complicated. We are going through things that we have never gone through before, three internationals in one year is a hell of an ask," he added.
In the women's 200m freestyle, the Netherlands' Marrit Steenbergen swam a personal best of 1min 56.36 to win with Wilby's compatriot and 2019 champion Freya Anderson taking silver and Germany's Isbael Marie Gose with bronze.
In the final race of the day in the Italian summer heat, the home crowd exploded in celebration as the hosts dominated the men's 4x100m freestyle final in a time of 3min 10.50.
Milak's Hungary were almost two minutes slower in second with Britain in third as France were disqualified for an illegal handover.
Earlier, Romanian David Popovici claimed a place in the men's 200m freestyle final after breaking the world record in the 100m on Saturday, beating Milak who was second.
Popovici, 17, finished in 1min 44.91 and will compete for another gold in Monday's late session but Milak will be missing from the race after having to settle for fourth place in his heat.