UFC 243 at Melbourne's Marvel Stadium on Sunday drew 57,127 people, eclipsing the previous best of 56,214 at the same venue for UFC 193, almost four years ago.

They witnessed the New Zealand-based Nigerian-born Adesanya floor Sydneysider Whittaker with a right hook in the final seconds of the first round

The interim champion ended the unification bout with a left hook in the second round, just a moment after taking a big right hand to his head.

"I told him in the octagon, I said 'I'll see you again definitely', Adesanya said.

"He'll definitely work his way up. He said 'probably two fights I'll see you again'."

While Whittaker said he would be up for a rematch, Adesanya's first defence is likely to be against No.2 ranked contender Paulo Costa of Brazil, who was at the fight.

"He beat me tonight but I'm 28 and this is my first loss in the division. I'm not going anywhere," Whittaker said.

Whittaker was adamant he could prevail in a rematch.

"I feel that I can beat him. I have the skill sets to beat him but we clashed heads and I came off second best and I got floored," Whittaker said.

"Hats off to him, he's a great striker."

"I wasn't in awe of his striking. I was very confident and I was having great success. I've got to work on that check hook defence."

It was Whittaker's first fight since June 2018.

He pursued Adesanya for much of the bout but neither man landed a lot of telling shots in the first round until Adesanya's big right at the end.

He showed great evasive skills, avoiding plenty of kicks and punches and was more efficient with his offence.

Whittaker did land a few right hand strikes, but said the taller Adesanya was tricky to hit and was more efficient.

Adesnaya said Whittaker grazed his lip, but he never felt in any danger.

"What did I tell you (in the leadup) - it's probably one of my toughest tests but I'll make it look easy,'" Adesanya said.

Adesanya improved his MMA record to 18-0 and won the undisputed title in just his seventh UFC bout, all of them inside the past two years.

It was Whittaker's first loss in 10 bouts and in more than five years, with his MMA record dropping to 20-5.

New Zealand's Dan Hooker scored a unanimous points win over higher ranked American lightweight Al Iaquinta in the co-main event.

Australian fighters had mixed fortunes.

Female featherweight Megan Anderson scored a first-round submission win in her first UFC fight in Australia, and welterweights Jake Matthews and Callan Potter each had a points victory.

Heavyweight Tai Tuivasa suffered a third straight loss and lightweight Jamie Mullarkey and flyweight Nadia Kassem also got beaten.

Australian Associated Press