
MacNeil, who won 100m butterfly gold at the Tokyo Olympics, clocked 25.25s to shave 0.02s off her previous mark, which was set at the previous edition of the championships in Abu Dhabi last year.
American Claire Curzan took silver, while Australia’s Mollie O’Callaghan bagged bronze.
Earlier today, France won the gold medal in the mixed 4x50m freestyle relay in a world record time of 1:27.33s, bettering the US’ previous time of 1:27.89s.
Melbourne is hosting the short course championships after Kazan was stripped of the event over Russia’s invasion of Ukraine.
The event began on Dec 13, and will run through to Dec 18.