Strong off the blocks, Dressel took an early lead and held off the challenge of defending champion Kyle Chalmers of Australia to win by 0.06 seconds. Dressel's final time was 47.02 seconds.
Dressel's victory in swimming's blue riband event was the most high-profile result on a night that saw a number of records splashed aside in the pool and rivalries renewed between Team USA and Australia, as well as medal table challengers China.
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Dressel looked wide-eyed as he took in the magnitude of his victory. Straddling the lane rope, he raised his index fingers on each hand, sending a message to those watching in the Tokyo Aquatics Centre and at home: No. 1.
The pressure and comparisons to Phelps did not cower the 24-year-old from Florida, who had never before won an individual gold medal at the Olympics.
After the legend retired, Dressel emerged as the world’s dominant swimmer. He lived up to the hype at an Olympics where several U.S. stars have faltered.
“I knew that weight was on my shoulders,” he said following the race, according to The Associated Press.
American swimmer Bobby Finke also won gold with a surprise win in the men's 800-meter freestyle Thursday. It was his first Olympic medal in his first Olympic Games.
The race was also the Olympic debut of the event, and followed Katie Ledecky's win in the first Olympic women's 1,500-meter freestyle race Wednesday.
Ledecky, meanwhile, got another shot at her Australian rival Ariarne Titmus, nicknamed the 'Terminator.'
Down 2-0 in clashes so far, Ledecky and Team USA got the better of Australia in the women's 4x200-meter freestyle relay. But in the end neither team prevailed, with China taking gold, U.S. silver and Australia bronze.
All three teams swam faster than the previous world record time.
China’s winning time was 7:40.33, beating the previous world record — set two years ago by Australia at the 2019 Worlds — by more than a second.
It was China's second victory in the Olympic pool and took the country's total of gold medals so far to 14, one more than the U.S.
But Dressel was the night's star.
Thursday's was his second gold at the Tokyo Games and his fourth career medal. He had won with his teammates in the 4x100-meter free relay in Tokyo earlier this week, and secured two other relay gold medals in the 2016 Rio de Janeiro Olympics.
“We do enjoy racing against each other and we do bring the best out of each other,” Chalmers said, according to the AP. “It’s almost a relief to get it done with now.”
Dressel fought back tears after Thursday’s race, saying he wasn’t sure his win had set in yet.
"It's a really tough year, it's really hard. So, to have the results show up, I mean — it really came together, so I'm happy," he said.
The Associated Press and Reuters contributed to this report.