RIO DE JANEIRO - Sweden's Sarah Sjostrom won the first of her three 100m butterfly worldtitles as a 15-year-old in 2009.

On Sunday, her wait to become Sweden's first female Olympic swimming champion ended, winning the 100m fly in a new world record time of 55.48sec.

Canada's Penny Oleksiak won silver (56.46sec) while defending champion Dana Vollmer of the United States took bronze (56.63sec).

Sjostrom went into the Olympic Aquatics Stadium as the world-record holder and eclipsed her mark of 55.64sec set at last year's world championships.

"The feeling is totally crazy," she said. "I didn't realise it was a world record. I knew I was the big favourite. I was under pressure, so I tried to focus on no disasters.

"Before the start I said to myself 'it's just a pool, it's nothing'. I know what to do. I was not so nervous, I was in a good mood today. I knew the 100m butterfly was my big chance."