Pereira and Adesanya have a history that stretches back several years to when they were both kickboxers in the Glory organization.
Brassen then defeated Adesanya twice, one of which via brutal knock.
The New Zealander has since gone on to become one of the biggest stars in martial arts as a champion in the world's largest MMA organization, the UFC.
Last year, Pereira was also contracted by the UFC, and after three straight victories, he got the chance to face his old rival last night in front of 20,845 spectators in a packed Madison Square Garden in New York.
"Feeling lucky"
Then he won via technical knockout 2.01 into the fifth round after shaking the champion with a streak.
On Twitter, a lot of other UFC fighters thought the referee stopped the fight too early as Adesanya, who led the fight on points with all judges, was still on his feet trying to defend himself.
- I feel lucky and I have worked so hard for this.
It was a very tough match.
A lot of people said I wouldn't be able to go five rounds, but just look at what I've just done.
I'm ready for what comes next, says Pereira.
Israel Adesanya's new match result reads 23-2 and it was his first ever loss at middleweight (84 kilos).
Previously, his only loss had come at light heavyweight in 2021 when he moved up a weight class to challenge for a second world title belt.
Pereira, who is all the more new to the sport of MMA, climbs to 7-1 with seven straight victories.
He has now become world champion in both kickboxing and MMA.