Steve Larkin / AAP News
Image: Delly Carr / Swimming Australia

The swimming superstar has produced an outstanding swim to break the world record as she takes aim at the Birmingham 2022 Commonwealth Games.

Ariarne Titmus feels invincible after setting a world record in the 400 metres freestyle.

And the Australian is now daring her great rival, American legend Katie Ledecky, to take up the challenge to get the record back.

Titmus took Ledecky’s 400m freestyle record at the Australian championships in Adelaide on Sunday night.

The 21-year-old Queenslander clocked three minutes 56.40 seconds, bettering the previous benchmark of 3:56.46 set by Ledecky at the 2016 Olympics.

“I believe that Katie is the greatest swimmer of all time,” Titmus said.

“I can’t put myself up next to her.

“What she has done for female swimming has been insane, she has been at this level for 10 years.

“To be in the conversation with her, I feel completely honoured. And I hope now this is going to keep the battle going and give her some drive.

“Hopefully we can see how much faster we can keep going.”

Titmus beat Ledecky for Olympic gold in the 200m and 400m freestyle finals at last year’s Tokyo Games and finished second to the American in the 800m final.

And Titmus said her Olympic success had led to a new-found outlook on swimming, and life.

“I am the happiest I have ever been outside of swimming, I am the happiest I have ever been in my life in swimming,” she said.

“Olympic gold was obviously my childhood dream.

“And I feel like I now have that invincibility in swimming and it has translated to my life outside of the pool.

“I am definitely not putting the pressure on myself that I used to but it’s still a healthy amount. That has been the trick to me swimming well.

“Just going out there completely fearless, swimming what I used to feel like when I was 16 and first cracked on to the national team and just going out there and surprising myself.”

The 21-year-old said she had Ledecky’s world mark in the back of her mind entering Sunday night’s final.

“I thought that if I went out there and did the best race I could with how I am feeling at the moment, the world record was definitely within my reach,” Titmus said.

“But … if you think about it, your race plan comes undone.

“You really have to think about the process. I think people don’t understand the 400 freestyle is very hard to put together, like the 200.

“It’s just getting faster and faster so you have got to have more speed and it’s about that fine balance between your endurance and your speed.

“And trying to nail that is still something I am trying to get as perfect as possible – I don’t think I will ever get there.”