She clocked a time of two minutes 03.14 seconds, slicing 0.21 seconds off the previous record, set by American Regan Smith at the 2019 World Championships in Gwangju, South Korea.
The triple gold medallist from the Tokyo Olympics already owned the 100 metres backstroke world record of 57.45 seconds, which she set at Australia's Olympic Trials in 2021.
"After the Olympics I found it hard to get up behind the blocks again," McKeown told New South Wales Swimming.
"I found a new love for the sport (training with coach Michael Bohl) and it just goes to show that a happy swimmer is a fast swimmer.
"I haven’t necessarily changed anything in my program or training wise. It’s just that I’m happier."
McKeown was part of the Australian gold-winning 4x100m medley team in Tokyo and is also the current Olympic champion in 100 and 200 metres backstroke.
