In one of the most anticipated female fights in UFC history, bantamweight champion Nunes (17-4) successfully moved up in weight and knocked out dominant featherweight Cris "Cyborg" Justino with an overhand right just 51 seconds into the opening round. The championship fight co-headlined UFC 232 at the Forum.
The victory makes Nunes, 30, the first female fighter to win UFC titles in multiple weight classes.
"Nothing was going to stop me from what I wanted to do tonight," Nunes said. "When she connected with a couple of punches, I just said, 'I'm going to walk right through her.'"
UFC president Dana White said the debate is over after Saturday's fight.
"She's the best ever," he said. "How can you deny it? That's what this fight was for. If you look at her résumé and who she's beat, she's the best ever. You can't debate that."
Justino, who fights out of Huntington Beach, California, has made a career out of bullying opponents against the fence and knocking them out in devastating fashion. Going into Saturday, Justino had won 20 consecutive fights, 17 of them by knockout. She has collected 10 first-round finishes in her illustrious career.
Known for her punching power at bantamweight, Nunes met fire with fire. She clipped Justino early with a right hand after knocking her off balance with a strong leg kick. As Justino looked to aggressively move forward, Nunes dropped her to a knee with a right hand.
Although she was clearly dazed by the shot, years of bullying came into play for Justino, and she refused to take a step back. As she moved forward again, Nunes rotated away from the fence, dropped Justino to her knees with a left hook and then knocked her out cold with an overhand right.
"Yeah, for sure," Nunes said when asked if she thought the fight would play out the way it did. "I said, 'This is for the title. I'm gonna be the first female two-champ in the UFC.' It happened. I told you. I told you."
It was Justino's first loss since her professional debut in May 2005. The Brazilian has said she has one fight remaining on her UFC contract, and she has discussed the possibility of transitioning into boxing.
"Today was not my day," Justino said. "I lost, you know, it happens in the fight game. It's not the first time I've lost, it's not the last time I'm gonna lose. It happens, you know. It's the fight game.
"Of course I'm not happy. Of course I had my heart broken. But I didn't cry, and I'm not gonna cry, because I did everything [I could]. Today was Amanda's day."
Said Nunes: "Cris is a great fighter -- nothing but respect. It was an awesome opportunity to share the octagon with her. I'm very thankful to her for this. I'm the new 'champ champ.' I said that before, and now I'm just achieving this dream.''