Popovici had eased into the final earlier with a new European record of 46.98 seconds but today the 17-year-old Romanian double world champion swam 46.86sec.
David Popovici broke the men's 100m freestyle world record to win gold at the European Championships in Rome.
The 17-year-old Romanian double world champion swam 46.86sec on Saturday to slice 0.05sec off the old mark set by Brazilian Cesar Cielo in the same pool at the 2009 World Championships in the era of buoyant body suits.
The fastest time in a textile suit had been 46.96 set by American Olympic champion Caeleb Dressel at the 2019 World Championships.
Hungary's Kristof Milak was second on Saturday with Italy's Alessandro Miressi third.
Popovici had eased into the final on Friday with a new European record of 46.98 seconds.
Only two other swimmers managed to dip under 48sec on Friday, Milak and Miressi in the other semi-final, but both were some way off Popovici.
In June, Popovici became the first man to complete the 100-200m freestyle double at the World Championships in nearly 50 years.
In a golden summmer, he also won three European junior titles in his home town of Bucharest.
The fastest 100 freestyle in history by the 17-year-old phenom David Popovici. 46.86. Absolutely insane.pic.twitter.com/NDYQiPXalC— Kyle Sockwell (@kylesockwell) August 13, 2022
Another 17-year-old world champion also added European gold on Saturday.
Italian Benedetta Pilato won the women's 100m breaststroke in 1:05.97, more than a second-and-half outside the world record set by American Lilly King in 2017.
Pilato was followed home by compatriot Lisa Angiolini and Lithuania's Ruta Meilutyte, the 50m world champion.
Pilato imitated her compatriot Federico Poggio, who won the men's 200m breaststroke on Friday.
Italy with the 1️⃣, 2️⃣ finish!— LEN - European Aquatics (@LENaquatics) August 12, 2022
Benedetta Pilato led the Women's 100m Breaststroke heats to qualify with a time of 1:05.77 🇮🇹
Swimming continues at 18:00 CEST. Catch the events LIVE on LEN TV 🖥 pic.twitter.com/QMnT0gj0a3
Swedish veteran Sarah Sjostrom won the women's 50m butterfly gold for the fifth time in 24.96. The 28-year-old is the only woman to go under 25 seconds in the events in a 50m pool.
France's Marie Wattel won silver in 25.33 with Maaike de Waard of the Netherlands a distant third in 25.62.
Frenchman Yohann Ndoye Brouard won the opening final of the evening when he took the men's 200m backstroke in 1 min 55.62 sec.
Ndoye Brouard had to swim his semi-final twice on Friday because of a problem with his starting block and ended up qualifying on time in an empty pool.
He beat Hungary's Benedek Kovacs in 1:56.03 and England's Luke Greenbank (1:56.15).