Rio Olympic champion and Tokyo silver medallist Kyle Chalmers was also firing on day four of the Australian trials in Brisbane, ensuring he will again contest the 100m freestyle in Paris this summer.
The 22-year-old McKeown, the reigning Olympic champion and world record holder, surged to the wall in 2:03.30s to reinforce her status as the overwhelming favourite at the July-August Games.
Her time was just a fingertip outside the world leading 2:03.14 she set last year.
“The first half of this meet I’ve been quite nervous, so I really just wanted to enjoy tonight,” said McKeown, adding that she was not aware of the crowd roaring her on.
“I was in my own little world, but I’ve got a ticket to Paris.”
Such was her dominance that she finished four seconds clear of second-placed Jaclyn Barclay – just 17 – who also qualified.
Veteran Emily Seebohm, swimming just months after having a baby, failed in her attempt to make a fifth Olympics, finishing fifth.
McKeown has now booked three individual events in Paris.
She swam the second-fastest 100m back of all-time on Tuesday, with her 57.41s just shy of her own world-record 57.33s.
That came a day after she posted the quickest 200m medley since the 2016 Olympics, another event where she will be a serious medal contender.
Special
Titmus is also in sparkling form.
She produced a sensational 200m freestyle on Wednesday to smash Mollie O’Callaghan’s world record, days after recording the second-fastest 400m ever.
Titmus is the Olympic champion in both those events, but only managed silver behind American legend Katie Ledecky in Tokyo over 800m and going one better is on her radar.
She comfortably qualified in 8:14.06, with only Ledecky faster in 2024.
Lani Pallister also made the grade, with her 8:18.46
“I just tried to forget about it (200m world record) as much as I could because I had a job to do here tonight,” said Titmus.
“To be completely honest, I’m disappointed with the swim, but have another chance in Paris to do better.”
Chalmers came through a stacked field to stop the clock at 47.75 and make a third Olympics, touching ahead of William Yang, Flynn Southam and Jack Cartwright who did not qualify but will join him on the relay team.
“Very special, very, very happy with that,” said Chalmers.
He will have his work cut out in France, with Chinese world record holder Pan Zhanle, ex-world record holder David Popovici, and reigning Olympic champion Caeleb Dressel all set to be in the mix.
Commonwealth champion Elizabeth Dekkers (2:06.01s) and Abbey Connor (2:06.82s) both made the grade for the women’s 200m butterfly.
But no one met the stringent Australian qualifying time – which is stricter than the Olympic standard – in the men’s 200m medley.