Australia's Emma McKeon became the first female swimmer to win seven medals at a single Olympic Games after completing the sprint double with victory in the 50m freestyle and then winning another gold in the women's 4x100m medley relay.
American Caeleb Dressel confirmed his dominance in men's sprint swimming, powering to victory in the 50m free to go with his 100m gold and clinching a fifth medal of the Games as Team USA triumphed in the men's medley relay.
There was more gold joy for the United States with Robert Finke completing the distance double, producing another late push to win the 1,500m freestyle to add to his 800m gold.
The United States ended what has been an enthralling swimming competition in Tokyo with 11 gold medals, five less than in Rio and London.
Australia won nine, their most swimming golds at a Games, and Britain left with four golds as part of a record haul of eight total medals.
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McKeon, who has pocketed four golds in Tokyo, swam the butterfly leg as part of Australia's 'Awesome Foursome' in the medley relay, with Cate Campbell's superb final leg pushing the United States into silver.
That saw McKeon join Michael Phelps, Mark Spitz and Matt Biondi as the only swimmers with seven medals at a Games. Russian gymnast Maria Gorokhovskaya, in 1952, is the only woman to have won seven in any other sport.
"It still feels pretty surreal. I never thought I would win two golds in one session ... I'm very proud of myself," she said.
Team-mate Campbell was full of praise for McKeon's performances in Tokyo.
"Full credit to Emma ... I think that we just need to acknowledge what an incredible job she has done," Campbell said.
"She walks away from these Games with four gold medals now and I honestly could not be happier for her. She is such an important part of this team and I think that needs to be recognised."
McKeon outsprinted the field in the 50m freestyle, with Swede Sarah Sjoestroem taking silver and Rio 50m champion Pernille Blume of Denmark bronze, and was then quickly back in the pool for the medley relay.
The Australians were second all the way to the final turn when Campbell pulled away from Abbey Weitzeil to secure the ninth gold medal for the country in the Tokyo pool -- eight of which have come from the women's squad.
Dressel, the 100m free and butterfly champion, completed his sprint double with a huge margin of 0.48 seconds over France's Florent Manaudou, the London gold medal winner and silver medallist in Rio. Bruno Fratus of Brazil took the bronze medal.
The 24-year-old Floridian then produced the defining butterfly leg in the United States' medley relay victory, powering ahead of Britain's James Guy to set up Zach Apple, who sped home on the freestyle anchor leg to touch first.
Britain took silver, to secure their most successful Games in the pool, with Italy taking bronze.
Just before Manaudou won silver, his partner Pernille Blume of Denmark secured 50m freestyle bronze to add to her gold in Rio, meaning the couple have won back-to-back Olympic medals.
Manaudou, 30, was powerless to stop Dressel, and waited poolside to watch Blume. The pair shared an embrace before dozens of cameras as she climbed out of the pool.
Manaudou said: "I'm happy for her, I'm happy for me and I'm happy because, yeah, it's never easy to be with someone who achieved a gold medal at the Olympics.
"Its pretty amazing that we both get medals tonight almost at the same time."
Duncan Scott became the first British athlete to win four medals at a single Olympics, taking gold in the men's 4×200 metres relay and silver in the 200m freestyle, 200m individual medley and 4×100 metres medley relay.