Caeleb Dressel of the United States won the men's 100m freestyle gold and compatriot Bobby Finke clinched the 800m free in a day of double American glory in the Tokyo pool.
World champion Dressel powered to victory an Olympic record time of 47.02, finishing six hundredths of a second ahead of Rio winner Kyle Chalmers of Australia, with Russian Kliment Kolesnikov taking bronze.
Australia's Zac Stubblety-Cook took gold in the men's 200m breaststroke on Thursday with a powerful late surge to the finish.
China gained their first gold in the Tokyo pool with Zhang Yufei winning the women's 200m butterfly to add to her silver medal in the 100m fly.
Dressel went into the race as favourite and led from rising star Kolesnikov at the turn before holding off a strong finish from Chalmers to touch first.
It was Dressel's fourth Olympic gold but his first in an individual event having picked up two relay medals in Rio and the 4x100m freestyle relay in Tokyo.
“I wasn’t worried about anything at all ... it means a lot, I knew the weight was on my shoulders," said Dressel.
Finke pulled off a surprise win ahead of Italian world champion Gregorio Paltrinieri, who led all the way until the 750m turn when German Florian Wellbrock moved in front for the last length.
But Finke then made his late move and powered home in a time of 7:41.87. Wellbrock faded but Paltrinieri did not, the Italian, who had been a doubt for the Games due to illness, touching 0.24 seconds behind Finke to take the silver.
Ukraine's Mykhailo Romanchuk took the bronze medal.
Finke said he had to push hard when he saw Paltrinieri was clawing his way back towards the finish.
"I noticed when I was about 10 metres out that he was catching a little ground and that was all the motivation I needed," said the American.
In the 200m breaststroke, Arno Kamminga of the Netherlands led at the 150m turn and was inside world record time as he fought with Finland's Matti Mattsson.
Stubbletly-Cook was third on the last turn, 1.2 seconds adrift of the lead, but then delivered an astonishing final lap to secure the country's fifth gold medal in the pool so far and the first for their men.
Kamminga was second, adding to his silver in the 100m breaststroke, with Mattsson taking bronze.
The gold was the first in men's breaststroke for Australia since Ian O'Brien in Tokyo in 1964, also in the 200m.
China's biggest gold medal hope Zhang delivered in style -- taking control from the outset as she set a new Olympic record time of 2:03.86.
Americans Regan Smith and Hali Flickinger took the silver and bronze medals.
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