LAS VEGAS — Julianna Peña quietly danced in her corner as bantamweight champion Amanda Nunes made the long walk to the cage for their title fight Saturday in the co-main event of UFC 269 at sold-out T-Mobile Arena.

For more than five years, Peña had waited for this moment since Nunes won the title at UFC 200 in 2016 by crushing her mentor and close friend, Miesha Tate. She’d believed against all odds that she’d get the job done.

Before she even was in the UFC, she heard UFC president Dana White was at Syndicate MMA in Las Vegas. She caught a cab and cornered White, whose sons were in a jiu-jitsu class.

“She introduced herself and told me she was going to fight for me and become a world champion,” White said.

On Saturday, the moment finally arrived. She was a massive underdog. At BetMGM, Nunes was a -1000 favorite, with Peña closing at +625.

Nunes walked to the Octagon as the widely acclaimed greatest fighter in women’s MMA history. But there were no nerves, no doubts, no worries for Peña.

“I was cool, calm and collected,” Peña said. “I was cool as a cucumber.”

She was buoyed by the support of her team and coaches, particularly head coach Rick Little. In 2019 in Nunes’ previous bantamweight title defense against Germaine de Randamie, Little was watching.

He told her, “You can beat her.”

And then, nearly two years to the day later, she did. Peña submitted Nunes with a rear naked choke at 1:02 of the second after besting her in a toe-to-toe slugfest, fulfilling her promise to White and completing a 13-year-old dream.

Until she defeated Nunes on Saturday, Peña hadn’t won back-to-back fights since taking her second in a row by beating Cat Zingano at UFC 200 on the Nunes-Tate undercard.

The victory was a reminder of why this sport is so popular. Anything can happen at any time.

“One of the great things about this sport, what makes this sport so incredible, is that when somebody is so big of an underdog [can win],” White said. “How many times have we been at these events where when the fight’s over, everybody’s looking at each other like, ‘Holy s***!’”

The card showed the agony and ecstasy of the sport. As Peña climbed to the top of the cage and raised her arms in exultation — the first time she’s ever done that, she said — Nunes was dejected in her corner.

And a bit later, Dustin Poirier was submitted in the third round of the main event, losing his lightweight title challenge when he tapped to Charles Oliveira’s rear naked choke.

Poirier had a great first round and felt he was about to become the new champion. A few moments later, he was trying to pick up the pieces.

“I’m going to continue to try to do good and be a better person every day,” a choked up Poirier said.

Peña followed him to the post-fight news conference and never stopped smiling. Her left eye was nearly closed, swollen as a result of the fierce exchanges she’d had moments earlier with Nunes.

The fight was the first time that two mothers had met for a UFC championship, but Peña became the first fighter who had given birth to win a belt.

“The UFC actually needs to create a new belt for me and it’s got to be ‘Baddest Mom on the Planet,’” Peña said. “I’m not trying to take anything away from Amanda; she’s a wonderful mother. But I gave birth to my daughter. I feel like for giving birth, I am the first Mom-Champ. That means a lot to me.”

She has plenty of options, though she may have destroyed others. The UFC is in talks with free agent Kayla Harrison, whom they wanted to match with Nunes at 145 pounds in what would have been a massive financial fight.

With Nunes losing, that puts that fight into jeopardy and perhaps even the UFC’s chances of signing Harrison.

But with one door closed — or at leasing closing — others opened. Peña is amenable to a rematch with Nunes at 135, but said she’s also interested in a bout at 125 with flyweight champion Valentina Shevchenko, who defeated her in 2017.

She didn’t want to think too much of what’s next immediately after the fight. She’d been in camp close to a year because the bout with Nunes was postponed from its original September date when Nunes got COVID-19.

So she wanted to spend time with her family and reflect on the enormity of what she’d accomplished.

“I have nothing to prove,” Peña said. “Everyone slept on me and I shocked the world.”