American Strickland taunted Adesanya in the closing seconds of the final frame, confident of victory after 25 minutes of stalking his opponent, defending brilliantly and using his boxing to force Adesanya to fight off the back foot.
Adesanya, who has ruled the roost as middleweight champ for most of the last four years, failed to find a way to break Strickland down and the Nigerian was caught several times by stiff jabs from Strickland that slowed him down.
"Oh my God, literally never in a million years did I thought I'd be here," Strickland said in an interview in the cage after UFC president Dana White wrapped the championship belt around his waist.
After giving him a hostile reception on his way to the octagon and cheering for Adesanya, who grew up in neighbouring New Zealand, throughout, the crowd hailed the new champion for his gutsy performance.
"The majority of my friends he's beaten pretty easily, so I was even kind of doubting myself, but I've gotta say to the fans, you guys motivated me," Strickland said.
Strickland set the course for victory with a thunderous right hand at the end of the first round, almost securing a knockout, and though Adesanya managed to make it to the break, he never really got going again after that.
Known for his creative striking, the Nigerian-born Adesanya became increasingly desperate as the fight wore on and he won only one of the five rounds, with the three judges awarding the rest to Strickland on identical 49-46 scorecards.
