American swimmer Ian Finnerty broke his own Summer Universiade record to claim 100 metres breaststroke gold in a thrilling battle with Russian Kirill Prigoda.
Finnerty yesterday qualified for the final by lowering Ukrainian Igor Borysik's record from the 2009 Universiade in Belgrade.
In tonight's final, he recorded a winning margin of 0.01 seconds as both swimmers ducked under his semi-final time of 51.51sec.
Finnerty was first to the wall at Piscina Scandone in 59.49, with Prigoda just behind.
Japan's Yuya Hinomoto took the bronze medal in 59.72.
There was more glory for the United States when Lisa Bratton reclaimed her 200m backstroke title in a one-two with compatriot Asia Seidt.
Having won the event in Gwangju in 2015, Bratton saw off Seidt - who broke the Universiade record in yesterday's semi-final - by setting a new mark of 2min 07.91sec.
Seidt also went quicker than her semi-final time but had to settle for silver in 2:08.56 as Britain's Chloe Gooding won bronze in 2:09.57.
Zijie Hu & Chunting Wu (CHN) take the top spot on the podium for the Mixed 3m Synchronised Final Diving. 💦🐬 #Napoli2019 #ToBeUnique #Universiade— FISU (@FISU) July 5, 2019
💻📱🖥 Watch the Universiade on https://t.co/8XfcaBi162 from 3 to 14 July! ☀🌋🍕 pic.twitter.com/yC0VlcXcYb
Tayla Lovemore set a national record to earn South Africa's first gold medal in the women's 50m butterfly.
She lowered Erin Gallacher's 26.30 record by 0.05 seconds to get the gold medal.
Japan's Ai Soma finished second in 26.38 and Jeong So-eun of South Korea won bronze in 26.41.
At Mostra d'Oltremare, China won both of the gold medals available as they clinched a fifth of six diving titles from two days of competition.
Lizhi Cao and Zigan Huang overhauled Mexican rivals Andres Villarreal Tudon and Jose Balleza Isaias to win the men's 10m synchronised platform title.
The duo had been in second place at the halfway stage before executing three superb dives to score 90.78, 82.14 and 80.64 points, respectively, and claim gold from the Mexicans.
The Chinese duo finished with 431.16 points as Tudon and Balleza Isaias were pushed into silver on 403.26.
Canadian pair Laurent Gosselin-Paradis and Ethan Pitman took bronze with 373.77.
The second Chinese medal at the diving pool was won in a fierce 3m synchronised mixed team contest with Russia.
Zijie Huang and Chunting Wu were tied with Egor Lapin and Evgeniia Selezneva after three rounds but put in two strong final dives to increase to five China's diving gold medal tally.
The duo top scored with 301.38 as Lapin and Selezneva took silver, scoring 287.40 points.
Carolina Mendoza and Adan Zuniga Ornelas from Mexico took the bronze medal with a score of 279.45 points.
Only 24 hours after Japan won the men's artistic gymnastics team gold medal, their women's team followed suit at PalaVesuvius Main Hall.
Hitomi Hatakeda, Aiko Sugihara and Asuka Teramoto were the stars of the show as they totalled 108.450 points to win gold.
Liliia Akhaimova, part of the Russian team who won gold at the 2017 Universiade in Taipei, had to settle for silver here with a team total of 107.450 points.
The bronze went to hosts Italy on 103.500, with controversial Torchbearer Carlotta Ferlito leading the Italian trio onto the podium.
Ferlito, once accused of making a racist comment towards American gymnast Simone Biles, was Italy's star with an individual total of 39.650 points.
At the 2017 Summer Universiade in Taipei, Japan won two golds from their 12 artistic gymnastic medals.
After just two events in Naples, they have already secured two golds.