The 16-year-old stopped the clock in 3.56.08 in Toronto, knocking 0.32 off the previous record. That had been set by Australian’s reigning Olympic champion Ariarne Titmus, who took her record off reigning world champion Katie Ledecky.
Subsequently, McIntosh is also now the Canadian, Commonwealth, and World Junior Record holder in the event – taking the last two accolades off Titmus and Ledecky respectively.
The giant trio of women’s freestyle swimming could all meet in the 400m free at the 2023 World Championships in Fukuoka, Japan this July, before another possible showdown at the Olympic Games Paris 2024.
It was the latest achievement in what has been a stellar 2023 so far for McIntosh, who broke three junior world records in three days at the TYR Pro Swim Series earlier this month.
The most difficult choice for the aquatic prodigy going forward could be which events to focus on given her impressive versatility.
She is also the world champion in the 400m individual medley and the 200m butterfly after taking out those titles in Budapest, aged just 15.
McIntosh, whose mother swam at the Olympic Games Los Angeles 1984, became the youngest individual world champion in swimming since Shiwen Ye in 2011.
According to Olympics