American Kate Douglass clinched her first Olympic gold medal by winning the women's 200m breaststroke final at the Paris Games on Thursday.

Douglass finished in two minutes, 19.24 seconds, more than half a minute ahead of reigning champion Tatjana Smith of South Africa.

Dutchwoman Tes Schouten took bronze, almost two seconds behind Douglass.

"For a while I wasn't sure if Olympic champion was going to be possible for me to say and now it's really exciting to see it happen," Douglass said.

The 22 year-old's time broke her own American record set earlier this year.

"I knew if I went a best time and went the American record, that would probably win the race," she said. "I could see on the turn where I was, so I kicked it into high gear. I couldn't tell if she [Smith] was going to catch me.

"I was trying to say calm and collected. I have a specific stroke count that I've done on a few of my best times, so I knew if I stuck to that it would probably be my best time."