Who is Ariarne Titmus, the Australian nicknamed the Terminator who beat Katie Ledecky?

Ariarne Titmus of Australia won gold in the women’s 400-meter freestyle on Monday, beating defending champion and world-record holder Katie Ledecky from the United States.

“Surreal,” said Titmus, who is competing in her first Olympics. “It’s the biggest thing you can do in your sporting career.”

Titmus, 20, is from Tasmania, a small island-state off the south coast of Australia. According to her profile on the Tokyo 2020 Olympics website, she began swimming at 7, and her success has earned her the nickname the Terminator.

Titmus joined the Australian Dolphins Swim Team in 2016, and a year later, went on to win a bronze medal in the women’s 4×200-meter freestyle relay at the 2017 World Championships.

At the world short course championships in 2018, an international swimming competition, Titmus won gold medals in the 200-meter freestyle and the 400-meter freestyle, where she also set a world record for the event with her time of 3:53.92.

That year, Titmus also won gold medals at the Commonwealth Games, a multisport event among the various nations of the British Commonwealth held every four years.

Her medal haul continued at the 2019 FINA World Championship in Gwangju, South Korea, where Titmus handed Ledecky her first-ever major international loss, when she won gold in the 400-meter freestyle.

At that same competition, Titmus went on to win gold with her team in the 4×200-meter freestyle, setting a world record in the process. Titmus also won silver in the 200-meter freestyle and bronze in the 800-meter freestyle.

Titmus’s win on Monday earned Australia its second gold medal in the Tokyo Games.

Titmus’s next race will be Tuesday at 10:30 a.m. in Japan (9:30 p.m. Eastern on Monday), where she will compete in the women’s 200-meter freestyle semifinal against the event’s Olympic-record holder, Allison Schmitt from the U.S.