Australia's Ariarne Titmus blew 400m freestyle rivals Katie Ledecky and Summer McIntosh out of the water and reclaimed her world record at swimming's world championships in Japan on Sunday.

Titmus came home in 3 min, 55.38 sec to win the title and take back the record that McIntosh had wrested from her in March this year.

Ledecky finished the race second in 3:58.73 but McIntosh could only place fourth, with New Zealand's Erika Fairweather taking third in 3:59.59.

"I was really excited for this race coming in tonight," said Titmus, who was going head-to-head with Ledecky and McIntosh for the first time since she won gold at the Tokyo Olympics two years ago.

"Me and Katie and Summer always put up a great fight and I'm glad that we could put on a show."

The race was one of the most hotly anticipated of the world championships on the opening night in Fukuoka.

It pitted Olympic champion Titmus against world record-holder McIntosh and defending world champion Ledecky.

But Titmus led the race from start to finish and looked comfortable in breaking McIntosh's previous benchmark of 3:56.08.

"Women's sport is really getting hyped up," said Titmus, who also won the world title ahead of Ledecky in South Korea in 2019.

"I just feel really blessed to be a part of it."

Titmus had added a little spice to the build-up by questioning McIntosh's ability to handle the pressure of the big occasion.

Ledecky had laid down a marker by finishing fastest in the morning heats ahead of Titmus and McIntosh.

Ledecky was aiming to add to her 19 world titles, already a record for a woman.

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