Belarus' Yuliya Nesterenko stormed through in the last 30 metres to take 100m gold from Lauryn Williams.
Nesterenko, the form athlete all through the heats, ran 10.93 seconds to take her first global title.
Williams led at 60m but Nesterenko stayed relaxed and powered past as Williams tied up under pressure.
Jamaica's Veronica Campbell took bronze, but former Olympic champion Gail Devers and France's Christine Arron failed to make the final.
Britain's Abi Oyepitan missed out on the final by one place.
"I am very, very happy," said 25-year-old Nesterenko.
"For six months I have been working and training very hard so I knew I could win."
Nesterenko came into the Games as an unfancied contender, despite posting some strong times in the build-up to Athens.
But the Belarussian insisted she had pointed to her potential when she clinched the bronze medal over 60m at the world indoor championships in March.
"I did not just arrive from nowhere," Nesterenko said.
"I was on the podium in Budapest."
Her win saw the first time since the 1980 Moscow Games - which the US boycotted - that an American had not won the sprint crown.