The Australian clocked 50.96 to win the women's 100m freestyle, lowering her previous PB of 51.02, over a second ahead of compatriot Madi Wilson in second.
McKeown is fresh off an incredible Tokyo 2020 performance where she won four Olympic gold medals to become the most decorated female swimmer at the Games.
She was cashing in her chips in Berlin too, that 100m freestyle gold stacking up on top of the 50m freestyle gold and 50m butterfly silver she bagged on days one and two respectively.
Another star of the Tokyo Games was on top of the world too: Canada's reigning 100m butterfly Olympic champion Maggie Mac Neil won gold in the Berlin 100m fly, while flying Dutchman Arno Kamminga pulled off a spectacular breastroke hat-trick and 18-year-old Matthew Sates had a day to remember.
Sates defeated Rio Olympic gold medallist Kyle Chalmers, who has won two golds in Berlin, and Danas Rapsys to the 200m freestyle title, before adding the 400m IM title for good measure, setting a second new World Junior Record in two days.
Maggie Mac Neil holds off Louise Hansson to claim 100m fly
Reigning Olympic champion Maggie Mac Neil was put to work by Sweden's Hansson in the 100m fly, the Swede swimming a 25.92 split - under world record pace - but the Canadian reeled her in.
The Tokyo 2020 champ clocked 55:30 for gold, Hansson took second place in 55.49, and Swiss swimmer Maria Ugolkova was third with 57.00.
Arno Kamminga's breastroke hat-trick
Kamminga leaves with fond memories of Berlin after a 200m breaststroke victory on Sunday meant a clean sweep for the Dutch flyer.
A double Olympic silver-medallist this summer, Kamminga claimed three gold medals in Berlin in the 50, 100 and 200 metre breast events.
Two World Junior records for Matt Sates
South African teenage sensation Sates swam a 1:40.65 200 free to leave Kyle Chalmers and Danas Rapsys thrashing in his wake, setting another Junior World Record.
Making it even more impressive was the fact that he did it in the same session as his 400 IM victory, just 24 hours after he broke the world junior record in the 200 IM.