Michael Phelps blew away Ryan Lochte and gymnast Simone Biles won her second gold as the United States took control of the Rio Olympics medals table on Thursday.
As golf made its long-awaited return and Fiji partied after a famous rugby win, Phelps was magnificent once again in retaining his 200m individual medley title.
The race was a last showdown between Phelps and Lochte but Phelps showed no mercy and won by nearly two seconds from Japan's Kosuke Hagino, with Lochte back in fifth.
Afterwards, the 31-year-old waggled four fingers to signify the four gold medals so far in Rio which have taken him to an incredible 22 Olympic titles and 26 medals altogether.
"I say this a lot, but every single day I'm living a dream come true. As a kid I wanted to do something that no one had ever done before and I'm enjoying it," said Phelps.
"Being able to finish how I won is just something very special to me and this is why you are seeing more and more emotion on the medal podium."
Simone Manuel dead-heated with Penny Oleksiak to share victory in the women's 100m freestyle and become the first African-American woman to win an individual Olympic swimming gold.
Ryan Murphy won the 200m backstroke and former sex abuse victim Kayla Harrison successfully defended her women's judo title as the United States leaped on the medals table with 16 golds, five ahead of China.
Teenager Biles, just days after inspiring the United States to victory in the gymnastics team event, conjured a sublime exhibition of acrobatics and tumbling to claim the all-around crown.
The 19-year-old is chasing five gold medals in Rio, and few would bet against the 1.45m (4ft 9in) Texan adding to her tally in the apparatus finals to come.
It was another flawless performance from Biles, whose prodigious talents have earned her comparisons to the legendary Nadia Comaneci, winner of five gold medals during the 1976 and 1980 games.
"I'm not the next Usain Bolt or Michael Phelps, I'm the first Simone Biles," she said, declining to embrace comparisons with other Olympians.
Biles' performance came on a day when golf returned to the Olympics for the first time since the 1904 games in St. Louis — England's Justin Rose marking the occasion with a hole-in-one.
Australian Marcus Fraser — who only became an Olympian after four higher-ranked countrymen declined — was the early pace-setter. He fired an eight-under-par 63 to take a three-stroke lead over British Open champion Henrik Stenson of Sweden and Canada's Graham DeLaet.
Another sport making a return over a long hiatus — rugby union — finished with Fiji's sevens team scoring the South Pacific nation's first ever gold medal.
The South Pacific islanders turned on the style in a dazzling 43-7 victory over Britain to delight a raucous crowd at the Deodoro Stadium and set off wild celebrations at home.
Germany has been fretting over its lack of success in Rio but struck gold in the men's and women's quadruple sculls and shooting to zoom up the medals table with four in all.
The men's crew of Phillipp Wende, Lauritz Schoof, Karl Schulze and Hans Gruhne defended their title in the men's quadruple sculls
Moments later Annekatrin Thiele, Carina Baer, Julia Lier and Lisa Schmidla claimed the women's title. Barbara Engleder won the 50m rifle three position contest for Germany's first gold in Olympic women's shooting.
Forty-year-old rower Katherine Grainger became Britain's most decorated Olympic woman athlete with a second place in the double sculls with Victoria Thornley, her fourth silver in five Olympics. The pair were narrowly beaten by Poland's Natalia Madaj and Magdalena Fularczyk-Kozlowska.
Dominant New Zealanders Eric Murray and Hamish Bond stretched an eight-year unbeaten streak in the men's pairs.
The spectre of doping also loomed over the athletics competition, which starts Friday, as the International Olympic Committee confirmed that a second Kenyan coach had been sent home from the Games for a doping offence.
Media reports named the offical as sprint coach John Anzrah, saying he had attempted to impersonate an athlete during a doping test.
With inputs from AFP