Emma McKeon locks in individual Paris berth with butterfly victory

Australia's most decorated Olympian has confirmed Paris will be her last Games, with Monday's swim in the 100m butterfly the chance to add another individual medal to an already unmatched haul.

McKeon shot clear early and finished in 56.85, the only swimmer on the podium to swim the qualifying time, with Alex Perkins clocking a 57.33 in second place, and Brianna Throssell 57.42 in third.

It makes 30-year-old McKeon the first woman to qualify for the Dolphins Olympic team in her 30s since Lisa Curry in 1992.

McKeon told Channel 9 post-race that it's always a relief to lock in an Olympic berth.

"I'm stoked. That's what the Olympic trials are about, trying to get yourself on the team," McKeon said.

"It's really nice to do that on the first night. It's been a long time on the team, I [first] made it in 2010 when I was 15, I was so young.

"Even with 15 years of experience on the national team, you still have doubts and you have to battle those and overcome them. It's completely normal.

"I chose to keep swimming after Tokyo because I felt I had more to give, but also because I wanted to see what I was capable of, both physically and mentally.

"Overcoming those self-doubts is all part of that."

McKeon will now turn her attention to the 50-100m freestyle double later in the week, events in which she claimed gold in Tokyo.

While she was the clear pace-setter in the butterfly event, both fields in the freestyle sprint double will be arguably the most stacked in the history of the Australian team.