Emily Seebohm of Australia qualified fastest in the 100-meter backstroke preliminaries on Sunday with an Olympic-record time at the London Games.
Seebohm touched in 58.23 seconds, lowering the old mark of 58.77 set by Kirsty Coventry of Zimbabwe four years ago in Beijing.
''I saw that I was ahead of the world record and I was just like, 'Don't get over your head. Just keep going and just go as hard as you can,''' she said. ''All I wanted to do this morning was to make it through. My goal was just to keep moving forward and now maybe the world record in the final, who knows?''
Missy Franklin, the 17-year-old American competing in her first Olympics, was second-quickest in 59.37 in her first individual event. She earned a bronze medal as part of the U.S. 4x100 freestyle relay on the first night of swimming Saturday.
Franklin is set to swim seven events in London.
''It was awesome watching Emily Seebohm break the Olympic record, that was unbelievable,'' Franklin said. ''It's going to be an awesome race tonight. She did such a good job, but I am really happy about how I did and I'll be focusing on that.''
Belinda Hocking of Australia was third in 59.61.
Ten of the 16 women qualifying for the evening semifinals swam under 1 minute.
Anastasia Zueva of Russia, the silver medalist at last year's world championships, was fifth. Current world champion Zhao Jing of China was ninth.
A pair of British swimmers had the home fans cheering loudly. Georgia Davies was sixth, while world-record holder Gemma Spofforth moved on in 12th.
Rachel Bootsma, the other American teenager in the event, was 11th.
Coventry, the silver medalist in the last two Olympics, barely advanced, grabbing the next-to-last spot in 1:00.24.
''I've been up and down coming into the competition with my knee and then pneumonia, so I'm just excited to be here,'' she said. ''I'm just enjoying my fourth Olympics and I'll see what I can do.''
Two-time defending champion Natalie Coughlin failed to qualify for her signature event at the U.S. trials last month.
Laure Manaudou of France finished 22nd and didn't advance.