Israel Adesanya is the UFC's new interim middleweight champion after a violent unanimous decision win over American Kelvin Gastelum in Atlanta.

A dominant fifth round performance from Adesanya saw him clinch the fight, with each judge scoring the fight 48-46.

The battle saw both fighters pocket an extra US$50,000 bonus, taking out fight of the night honours alongside the main event in which Dustin Poirier beat Max Holloway to win the interim lightweight title.

"I was thinking 'we're going to die right here you and me'," Adesanya said of the fight. "It's kind of scary to say, but I was willing. I was like 'if he takes me out he takes me out, but I'm willing to die right here'.

"To all those people saying I can't take a shot, come on - he couldn't even put me away."

Anyone who wanted to see Adesanya take a heavy shot got their wish in the bout, with the first Kiwi-based UFC champion admitting Gastelum rocked him a few times during their five round epic.

Adesanya was tagged as early as the first round, and again in the fourth when Gastelum connected with a smart head kick and sent the Kiwi back peddling.

But Adesanya remained composed and pummelled the American in the fifth round to take the win.

UFC President Dana White places the interim middleweight championship belt on Israel Adesanya after defeating Kelvin Gastelum. Photo / Getty

"We knew what we did, we knew what we shared in that space. It was special," Adesanya said.

"These are legendary moments in time and history, and I'm so grateful to be a part of it."

Adesanya and Gastelum met with the interim belt on the line as a result of events in February.

Gastelum was scheduled to challenge for the middleweight title against Australian champion Robert Whittaker in Melbourne in February. However, Whittaker was forced to withdraw the morning of the bout after being rushed to hospital with a hernia. On the same card, Adesanya beat Brazilian legend Anderson Silva in a No 1 contender's match.

Booking an interim bout while Whittaker works towards his return later this year allows the UFC to honour both title shots without making one of the athletes wait.

It was a slow start for Adesanya, who looked to feel out Gastelum in the opening round. The American closed the distance extremely well to open the bout and was much more aggressive.

The second round was a different story as Adesanya began to fire. Peppering Gastelum's leading leg with kicks and launching head kick after head kick, it began to open holes in the American's guard. The Kiwi planted several good shots in the round, one sending Gastelum to the floor.

Losing the striking game, Gastelum began to search for a takedown.

It was during the third round when Adesanya scurried away after being taken down that Gastelum got the look in his eyes - the look of a man who underestimated his opponent.

Israel Adesanya elbows Kelvin Gastelum in their interim middleweight championship bout. Photo / Getty

But the American showed fight to take the fourth round, leaving everything on the line in the fifth.

But the final round was all Adesanya. Unlucky not to get a stoppage, he floored Gastelum a number of times and dominated the round to take the win and leave Atlanta with gold around his waist.

"I got a clean elbow in and I was hearing 'stop the fight, stop the fight' so I just kept on throwing. I didn't care, I just wanted to finish it.

"I was willing to die, so I was also willing to kill."

Adesanya is expected to go on to fight Kiwi-born middleweight champion Whittaker when he is back to full health, which is expected to be around August.