Portugal Colonial - O'Callaghan beats McKeon in clash of Olympic and world champions

The 19-year-old touched in a sizzling 52.63 seconds to beat a top-notch field.

Shayna Jack (52.64) hit the wall second ahead of seven-time Tokyo Olympic medallist McKeon (53.22) in a race that also featured returning veteran Cate Campbell.

Campbell, who has won eight medals over four Olympics, including four gold, was mulling retirement after Tokyo, where she took 100m bronze behind winner McKeon.

But she returned for her first major event since then to finish fifth in 53.78, with her eye on the world championships in Japan this year and a fifth Olympics in Paris in 2024.

"It hurts, but great to touch the wall," said O'Callaghan, whose time was quicker than the 52.67 that won her gold at the world championships in Budapest last year, an event McKeon skipped.

"I'm just so happy I get to have an awesome training mate in Shayna. It's been working out really great."

Australia's world championship trials are in Melbourne in June.

Kaylee McKeown, who shattered the 200m backstroke world record last month, also raced the 100 free and came eighth.

She earlier won the 200m medley in a personal best 2:08.16, second only to Canadian sensation Summer McIntosh this year and quicker than the pace that earned her silver in Budapest in 2022.

Swimming royalty Ariarne Titmus, whose 400m freestyle world record was broken by McIntosh last month, won the 800m freestyle in 8:20.19 ahead of world short-course champion Lani Pallister.

Titmus dethroned Katie Ledecky in the Olympic 200m and 400m freestyle but could only finish second to the American great over 800m.

In other events, 200m breaststroke world record holder Zac Stubblety-Cook touched in 1:00.07 to win the 100m race, while emerging 19-year-old Samuel Short stunned world champion Elijah Winnington to claim the 400m freestyle title.

Short's 3:42.46 was not only a personal best but easily the quickest in the world this year, and the 10th fastest in history.

"Obviously, I'm next to the world champion so I really tried to take it out with him," said Short. "Nearly a two-second PB, I was not expecting that."

R.J.Fidalgo--PC