Simone Manuel of the United States won the women's 100m freestyle final at the world championships on Friday to add to her Olympic gold from Rio de Janeiro.
Manuel touched the wall at 52.27 seconds with Sarah Sjostrom of Sweden, the world-record holder, at 0.04 back while Pernille Blume of Denmark took bronze at 0.42.
"It was tough. My legs were burning, I really had to dig deep and get my hands on the wall first," said Manuel, 20, who actually shared Olympic gold with Canada's Penny Oleksiak last year.
"I always think I have a shot -- that's what makes me the swimmer I am.
"I know how to rest and try to get my hand on the wall first.
"I had confidence in the training I had done and in my performance going into the race."
Sweden's Sjostrom, who won the 100m butterfly world title on Monday, the day after breaking the women's 100m freestyle record in the 4x100m relay, was disappointed with silver.
"It's sad when I can't do it," said Sjostrom.
"I went out fast, it felt really good in the first 50m, but I'm totally destroyed -- now there's so much pain in my muscles."
There was little joy for Australia in the final as defending champion Bronte Campbell was seventh at 0.91 while compatriot Emma McKeon was last at 0.94.