What you need to know:
- The 24-year-old timed 2min 18.95sec to better the 2:19.11 set by Denmark's Rikke Moller Pedersen in 2013.
- America's Lilly King was second in 2:19.92 with her team-mate and training partner Annie Lazor third in 2:20.84.
South African Tatjana Schoenmaker said it felt "so unreal" after she smashed the long-standing women's 200m breaststroke world record to win Olympic gold Thursday.
Schoenmaker timed 2min 18.95sec to better the 2:19.11 set by Denmark's Rikke Moller Pedersen in 2013.
It made her the first female South African to win an Olympic swimming gold since 1996, when Penny Heyns swept the women's 100m and 200m breaststroke.
Schoenmaker wore a look of disbelief as she looked up at the results board before breaking into tears as she was embraced by her rivals at the Tokyo Aquatics Centre.
"It's still so unreal," she said afterwards. "I think my emotions in the pool showed I was pretty shocked."
This was Schoenmaker's first Olympics after she just missed out on qualification for Rio. The 24-year-old won silver in the 100m event and signalled her intent for the world record by going close in the heats.
It was the third world record in the Tokyo pool, but the first in an individual event after Australia's women set a new mark in the 4x100m relay and China did the same in the women's 4x200m relay.
"If I could just make the final, that's what I've said ever since I knew I was coming," said Schoenmaker.
"I missed 2016 by a split second on the day at trials and it sucked and it wasn't a very happy moment but everything happens for a reason and to be honest I wasn't ready at that time.
"But I had a fall and my fall was quite big, so I had to start learning to love the sport again and knowing my goal was 2020.
"It's so weird to actually be here. You're so used to watching the Olympics on TV that it doesn't feel real. You see the logos and stuff but it hasn't sunk in and I'm glad it hasn't because then I'd probably be crying more."
America's Lilly King was second in 2:19.92 with her teammate and training partner Annie Lazor third in 2:20.84.
"I've been shocked the world record hasn't been 2:18 until this point, she's been swimming so well," said King. "I'm genuinely excited for her."
King went out fast and turned first at both the 50m and 100m mark before Schoenmaker made her move, reeling in the American to touch first.
Despite missing gold, it was an improvement for King who placed 12th at the Rio Olympics.