Ankalaev came into the bout unbeaten since 2018, winning 11 fights, and gained redemption for a title slip-up in 2022 when a split draw with Jan Blachowicz saw him miss out on gold.
Following a now-trademark intense stare down from Pereira during the introductions, the Brazilian opened the contest with a succession of leg kicks that became a theme of the early stages.
By the end of the first round, Ankalaev was sporting redness on his calf, but he found success in the second round with some punch combinations, before rocking Pereira with a straight left before the bell.
The defending champion recovered well midway through the fight, continuing his relentless leg-kicking approach, while Ankalaev responded with punches and some front kicks of his own.
The Russian then gained control with his grappling, wearing Pereira down against the cage, which left the Brazilian breathing heavily heading into the final stages of a close contest.
Pereira landed leg kicks and a high kick before a jab stunned Ankalaev, but the Russian finished the fight controlling the action against the cage once more.
Both fighters raised their arms in the air in expectant triumph, but it was Ankalaev who was given the nod.
Defeat ends a remarkable run at light-heavyweight for Pereira as he missed out on a fourth title defence inside a year, while Ankalaev claimed his 12th straight victory.
“I knew it would be a war. He put some pressure on in the second round, but putting me up against the cage, he didn’t really do anything,” said Pereira.
“I’m going to keep training. I feel good, I’ll have a few days off and then get back in training. This is my life.”
The co-main event saw American Justin Gaethje win an entertaining contest with Azerbaijan’s Rafael Fiziev by decision.
The 36-year-old was fighting for the first time since being stopped by Max Holloway in a highlight-reel knockout one year ago, and returned to winning ways with an accomplished striking display.
