'Oh my god': Swimming world goes bonkers over Ariarne Titmus moment

Ariarne Titmus sent the swimming world into meltdown on Sunday night after breaking Katie Ledecky's world record in the 400m freestyle.

The Aussie supertstar took her great rival's world record at the Australian championships in Adelaide, before challenging Ledecky to try and win it back.

'PATHETIC': Kyle Chalmers lashes out over 'love triangle' claims

'INSANE': Aussie young gun's world record stuns swimming world

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 of her American rival.

"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 in the 200m and 400m freestyle finals at last year's Tokyo Olympics, while also finishing second to the American in the 800m final.

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."

Swimming world erupts over Ariarne Titmus feat

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

“I never thought at this meet post the Olympics I‘d be swimming faster than the Olympic trials and the Olympic Games. I guess if you keep surprising yourself, it keeps the sport interesting," she said.

“Oh my God, I mean ... I think the biggest thing since the Olympics was that Dean (Boxall) said to me, you know, I have this freedom, the pressure’s off your back.

“I’ve just loved swimming in the past six months and I think going into training with no pressure, just enjoying the sport, it’s underrated how important that is.

“Coming here with no pressure other than the pressure I put on myself - which is still pretty high - it’s fun to come here and swim like that.

"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.

"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."

Swimming fans and commentators were left gobsmacked by Titmus' world record.

with AAP

Click here to sign up to our newsletter for all the latest and breaking stories from Australia and around the world.