Dual Olympic gold medallist Ariarne Titmus has recorded the fastest time this year to win the women's 200m freestyle final at the Australian Swimming Championships in Adelaide.

Titmus's time of 1:53:31 was faster than her gold medal-winning time at the Tokyo Olympic Games and her second fastest time.

The 100m champion Mollie O'Callaghan was second and Madison Wilson third.

Titmus conceded breaking the world record set by Federica Pellegrini in 2009 during the supersuit era was in the back of her mind after her teammate broke the 200m breaststroke world record on Thursday night.

"It was, like after watching Zac (Stubblety-Cook) and hearing Zac speak, you know I said to him, 'I kind of feel the exact same way in my swimming at the moment' – very free, just enjoying like a weight's been lifted off my shoulders," she said.

"I think it's definitely one of the more challenging world records," she said of Pellegrini's 2009 swim.

"Her back end in that race would have been insane — I think she had three suits on or something — so, even to be anywhere near that realm, I'm happy with the swim," Titmus said.

Titmus said she didn't get back into training after the Olympics until December.

"I'm really proud of how I've handled it post-Olympics," she said.

The Australian Swimming Championships are doubling as the trials for the world championships in Budapest in June and the Commonwealth Games in July.

Titmus said she didn't think she would be swimming as fast as she is now but has decided not to contest the world championships, preferring to concentrate on the Commonwealth Games with a view to the Paris Olympics in 2024.

Triple Olympic gold medallist Kaylee McKeown won the Women's 100m backstroke but couldn't threaten her own world record set last year.

Her time of 58:49 was almost a second behind her time set at the Australian Olympic trials at the same pool.

Mollie O'Callaghan came second, while Minna Atherton came third.

Asked if she was happy with the swim, McKeown said, "I don't know about that."

McKeown confirmed she will swim the 100m and 200m backstroke at the World Championship and will add the 400m individual medley at the Commonwealth Games in Birmingham.

The women's 100m freestyle champion, 18-year-old Mollie O'Callaghan had an exceptional night coming second in both the 200m freestyle and the 100m backstroke.

"It's absolutely been crazy this meet, I didn't expect this much to happen so quick, but I'm really happy with the results so far," she said.

She said she was getting pushed by Titmus and McKeown.

"I room with Kaylee, and I've gotten so close to the girls and it's so amazing to see how well they've done," she said.

She plans to swim in the 100m and 200m freestyle races at the world championships as well as the 100m backstroke.

Zac Stubblety-Cook followed up his World Record in the men's 200m breaststroke by winning the 100m race, but said it wasn't easy sleeping afterwards.

"I got to sleep, I was pretty wrecked by the time I got home, and then like four o'clock I was like all of a sudden awake again – yeah, it was a bit surreal," he said.

Joshua Yong came second, and Samuel Williamson was third.

In other results, Brendon Smith won the men's 200m individual medley final from Se-Bom Lee and Joshua Collett.

Jenna Strauch won the women's 200m breaststroke final from Abbey Harkin and Taylor McKeown – Kaylee's older sister.