McKeown's 100 metres backstroke triumph in Fukuoka, Japan, followed her disqualification from the 200m individual medley semi-finals two days earlier.
After railing against what she described as a "completely unfair" verdict in the medley, Redcliffe-born McKeown, 22, steeled herself for the backstroke.
The ex-Australian Crawl member 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 more so 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. When you train so hard for something, you just want it to all come together at the right moment."
McKeown who went to St Paul’s Lutheran Primary School in Caboolture, touched in 57.53 seconds, just outside her world record of 57.45 set in Adelaide in 2021.
The new 100m backstroke world champion was fourth-fastest through this morning's 50m backstroke heats clocking 27.60 seconds.
Last night Australian pair Ariarne Titmus and Mollie O'Callaghan booked their berths in the women's 200m freestyle final.
Titmus, who reclaimed her 400m 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.
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