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.

Titmus came home in 3 min, 55.38 sec to win the title on Sunday 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."

Anticipated Showdown

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.