Kate Douglass of the United States held off the South African favourite Tatjana Smith to win a thrilling women's 200m breaststroke gold at the Paris Olympics on Thursday.

Defending champion Smith established an early lead but Douglass was impressive at the turns as she finished in a time of 2min 19.24sec. Tes Schouten of the Netherlands took bronze.

The 22-year-old Douglass was the silver medallist in the 200m breaststroke at the 2023 and 2024 world championships.

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

"I feel like I was just trying to stay calm and collected.

"I feel like the 200m breast, I pretty easily can stay relaxed before it, just because I have a specific race plan and I know that if I stick to that, it's probably going to go pretty well," she said.

"I could see on the turn where I was, so I kicked it into high gear. I couldn't tell if she was going to catch me," she added of rival Smith.

The victory is Douglass's third Olympic medal following bronze in the 200m medley in Tokyo and silver in the 4x100m freestyle relay in Paris.

"I'm really excited to be able to call myself an individual Olympic champion and I'm really excited to get a gold for Team USA and help their medal count," she said.

Smith, who won gold in the 200 breaststroke in Tokyo under her maiden name Schoenmaker, and gold in 100m breaststroke earlier this week, said she would now bow out of the sport at the age of 27.

"That was an amazing race, so to end it off with a silver, but with a fight. That's the best way to end it," she said.

She leaves the sport with two Olympic gold and two silvers.

There was more disappointment for American Lilly King.

After missing the podium in the 100m breaststroke by 0.01 seconds, she finished last.