Kaylee McKeown has never known such nerves before capturing Australia’s fifth gold medal at the world championships in Japan.

McKeown’s 100 metres backstroke triumph in Fukuoka on Tuesday night follows her disqualification from the 200 metres individual medley semi-finals.

After railing against what she described as a “completely unfair” verdict in the medley, McKeown steeled herself for the backstroke.

She succeeded, coming within 0.08 seconds of her world record, but only after overcoming an unusually strong bout of nerves.

“I was very, very nervous heading in, probably moreso than I have ever been,” McKeown said.

“It was just to real testament myself dealing with what I have over the past few hours.

“Nerves just mean that you care about what you’re doing.

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“When you train so hard for something, you just want it to all come together at the right moment.”

McKeown touched in 57.53 seconds, just outside her world record of 57.45 set in Adelaide in 2021.

Also Tuesday night, Australian pair Ariarne Titmus and Mollie O’Callaghan booked their berths in the women’s 200 metres freestyle final.

Titmus, who reclaimed her 400 metres freestyle world record on Sunday night, secured lane four in the medal race by clocking one minute 54.64 seconds.

“I just had to do the job tonight, get through, try to get the middle lane,” Titmus said.

“I did what I had to do, and happy with it.”

Canada’s Summer McIntosh (1:54.67) was second-quickest with O’Callaghan (1:54.91) third-fastest into Wednesday night’s final.

Earlier, the legend of American Katie Ledecky grew yet again with another victory in the women’s 1500 metres freestyle.

The triumph was Ledecky’s fifth world title in the event and 20th overall.

Ledecky logged the third fastest time ever, 15:26.26 – she now holds the top 16 times in history over the distance.

With Italian Simona Quadarella (15:43.31) a clear second, Australia’s Lani Pallister held third spot and turned with 100 metres remaining in the bronze medal position.

But Pallister was overtaken by China’s Bingjie Li and Anastasiia Kirpichnikova from France, with the Australian fifth in 15:49.17, some 0.21 seconds outside her personal best.

In the men’s 50 metres butterfly semi-finals, Australia’s Sam Williamson snuck into the medal race.

Williamson touched in 27.06 seconds and was ranked eighth – one-hundredth of a second ahead of ninth.