Sixteen-year-old Canadian smashes Ariarne Titmus' 400 metres freestyle world record

A 16-year-old Canadian has fired a warning shot at Olympic champion Ariarne Titmus, breaking the Australian's 400 metres freestyle world record.

Summer McIntosh stopped the clock in 3:56.08 at the Canadian national trials in Toronto, more than three-tenths of a second inside the mark set by Titmus.

McIntosh broke down in tears as the enormity of the moment sunk in.

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"I'm not a crier," she told CBC Sports after the race.

"It's absolutely incredible. I'm not an emotional person. But I was hit with so much emotion. Pure euphoria right now. I'm just so grateful for everyone who got me to this point."

"Over the past few years I've put my life into this. To be the best I can be. To achieve something like this, it was very unexpected. It was never in my dreams to do this tonight or even a few years ago. This just blows my mind."

McIntosh finished fourth behind Titmus as a 14-year-old at the Tokyo Olympics, and second behind Katie Ledecky at the 2022 world titles in Hungary. This swim marks her as the one to beat in Paris in 2024, when she'll still only be 17-years-old.

The trio are all expected to feature at the world titles in Fukuoka in July.

"I'm not really sure what to say right now," her coach, Brent Arckey said.

"I'm trying to hold it all in. But celebrating her. This is a special thing.

"I've seen her do some really special stuff in practice. I'm just super proud of her. She's one of the best racers I've ever seen."