Billed as one of the biggest fights in Australian history, the UFC 243 main event began with Whittaker leaping in on Adesanya and throwing heavy shots.
But despite the pressure, the undefeated 30-year-old managed to stay composed during the barrages and in the final seconds of the first round, Adesanya stunned the all-time record UFC crowd of 57,000, returning fire with a devastating uppercut that dropped Whittaker.
Saved by the bell, The Reaper appeared groggy on his feet when the bell rang at the beginning of the second round.
Struggling to contain the speed and accuracy of Adesanya's attacks, The Last Stylebender took control of the Trans-Tasman tussle, landing a right-left combination that would see Whitter hit the canvas for the second time, officially ending the fight by knockout and extending the new champion's win streak to 18-0.
"Backstage I was so calm, I thought why do I feel this calm? I was so relaxed, I thought, should I be feeling this relaxed?" Adesanya told Xinhua after the match.
"But I think I just used my energy properly. I was able to control it and channel it at the right moment which was inside the cage."
"And I knew he [Whittaker] would start fast and then fall over himself. [My coaches told me] what makes him great also makes him vulnerable and susceptible to a lot of things."
Classy in defeat, Whittaker told reporters although it was a difficult loss, he aims to get back in the cage as soon as possible and take on the world's best.
"I went out there, I showed my heart, I showed my skill set and I came off second best tonight," Whittaker said.
"When you are fighting at this high level, every fight is on the line. We are walking a tightrope out there. Everybody can beat everybody."
"In the first round I was hitting him, I was hurting him, I was doing damage. I felt like I was controlling the fight and then I just got caught."
In other main card contests, New Zealand lightweight Dan Hooker upset top American contender Al Iaquinta via unanimous decision. Moldovan Heavyweight Sergey Spivak was too strong for local Aussie favorite Tai Tuivasa, finishing the fight in the second round with an arm triangle choke. Brazil's Dhiego Lima outpointed New Zealand hitter Luke Jumeau in the welterweight division. While Cape Verde heavyweight Yorgan De Castro scored a shock first-round knock-out victory against New Zealand's Justin Tafa.
END/XINHUA/UNB/TZ