Tom Daley finally ended his wait for an Olympic title with diving gold alongside Matty Lee, while British team-mates Adam Peaty and Tom Pidcock were also crowned champions as day three in Tokyo became 'Magic Monday' for Team GB.
Daley and Lee edged out China for victory in the synchronised 10m platform event, 13 years after the 27-year-old - a two-time bronze medallist - made his Games debut in Beijing.
In the early hours of day three, swimmer Peaty had become the first British swimmer to defend an Olympic title with his dominant victory in the 100m breaststroke.
Less than half an hour after Daley and Lee's gold, cyclist Pidcock added a third to Team GB's tally, dominating the men's cross-country mountain biking.
In taekwondo, Lauren Williams took silver after a closely fought loss to Croatia's Matea Jelic in the final of the women's -67kg.
Earlier, Britain's Alex Yee cemented his position as the new star of British triathlon with a silver medal, as Jonny Brownlee placed fifth.
The haul left Great Britain fifth in the medal table, with hosts Japan leading the way ahead of the USA.
Elsewhere, Japan's Momiji Nishiya won women's street skateboarding gold at just 13 years old.
Olympic organisers say a tropical storm will hit Tokyo on Tuesday but it is not expected to cause much disruption to the Games.
Rowing and archery events have already been moved because of the anticipated strong winds, but there are no plans to make any other changes to the schedule unless the forecast alters.
Tom Daley is competing in his fourth Olympics after Beijing 2008, London 2012 and Rio 2016Here's some of Monday's other news:
Daley wins first Olympic gold with Lee
Daley was just 11 when he told the BBC: "I want to get to the Olympics and win a gold medal." Sixteen years on, that dream is now a reality.
Daley and 23-year-old Lee, who was making his Olympic debut, performed impeccably throughout the synchronised 10m platform event, moving top of the leaderboard after four dives.
They finished with a total score of 471.81, leaving China's Cao Yuan and Chen Aisen with too much to do and they took silver with a tally of 470.58.
"That moment, being about to be announced as Olympic champions, I was gone. I was blubbering," said Daley.
Peaty defends Olympic title
Adam Peaty: Team GB star wins 100m breaststroke gold at Tokyo OlympicsVictory was expected for Peaty, given he has not lost over 100m for more than seven years, including his first gold in Rio five years ago.
Though he was unable to break his own world record of 56.88 seconds in Tokyo, he still finished more than 0.6secs quicker than the Netherlands' silver medallist Arno Kamminga, with Italy's Nicolo Martinenghi taking bronze.
Peaty touched the wall in 57.37, the fifth fastest time in history, but compatriot James Wilby could not join him on the podium, finishing in fifth place.
Peaty has won the 100m breaststroke at the past three World Championships, broken the world record five times and is the only man to have swum it in under 57 seconds.
"I haven't felt this good since 2016. It just means the world to me," said the 26-year-old.
Pidcock wins mountain bike cross-country gold
Cyclist Pidcock had prepared for Tokyo's brutal temperatures by training in a heated tent at home and it paid off.
He finished 20 seconds clear of the rest of the field in Izu, with Swiss world number one Mathias Flueckiger taking silver and David Valero of Spain winning bronze, to take Britain's first gold in mountain biking.
The 21-year-old, who has world titles in cyclo-cross, road and mountain bike events at under-23 level, had surgery on a broken collarbone at the start of June but returned to training just six days later.
When asked how it felt to win gold, Pidcock told Eurosport: "Not real, really. It's pretty crazy that I became an Olympian and I was trying to tell myself at the start of the race it's special just to be here."
Silver lining for Williams and Yee
For the second day running, Team GB boasted a taekwondo finalist and the result was silver again - with Welsh fighter Williams going down 25-22 to Croatia's Jelic.
Williams led with just 14 seconds left before Jelic came back right at the end to snatch the gold medal.
"I went out there to win, but I am very happy with how I performed all day. An Olympic silver medal is not bad, is it?" said Williams.
In the triathlon, Yee led for much of the 10km run before Norway's Kristian Blummenfelt produced a stunning breakaway in 27C heat and high humidity to win gold by 11 seconds.
"I am just a normal guy from south-east London - dreams really do come true," Yee told BBC Sport.
The event - which was moved to the early hours in Tokyo to avoid the worst of the heat - had to be restarted after a boat blocked around half of the athletes as they entered the water.
