American Dana Vollmer won the women's 100m butterfly Olympic gold medal Sunday, clocking a world record of 55.98sec for a crushing victory over China's Lu Ying.
Vollmer became the first woman to break through the 56-second barrier as she added the Olympic gold to the world title she claimed last year.
She bettered the previous world record of 56.06sec set by Sweden's Sarah Sjostrom on July 27, 2009 at the World Championships in Rome.
"I just relied on my strengths," Vollmer said. "Just set it up well, passed a few people and charged it home.
"I was delighted to get a record and be the first female to go under 56 seconds. I can have a better finish, so I know I can go faster."
Vollmer, who has been inching toward the record throughout the summer, was third at the turn, but burst off the wall and powered home to beat Lu by 89-hundredths of a second.
Lu came from fourth at the turn to take silver in 56.87 while Australia's Alicia Coutts rallied from last at the turn to take bronze in 56.94.
Vollmer has now well and truly laid the ghost of 2008, when she finished fifth in the 100m fly and seventh in the 200m free at the US Olympic trials and failed to make the Beijing team -- four years after she earned relay gold as a teenager in Athens.
"I knew I was in the lead, but I didn't know if I had the world record like I wanted," said Vollmer, whose parents and husband were at the Aquatics Centre to share in her achievement.
"It was everything I could have dreamed it would have been," she said.
Coutts, who had already claimed gold as part of Australia's 4x100m freestyle relay team on Saturday, said she could have finished even stronger if she hadn't choked on water with 15m remaining.
"I was happy to finish third in the end," she said. "If I had a perfect race I could have got silver. It was very fast."
Sjostrom was fourth and Denmark's Jeanette Ottesen Gray, who led at the halfway stage, faded to finish sixth.