Ronda Rousey's UFC comeback didn't even last a minute.

Amanda Nunes won the bantamweight title fight in Las Vegas on Friday night in only 48 seconds, destroying Rousey in her first fight in 13 months.

Rousey never managed to get her footing against Nunes, who rocked Rousey with her very first punches.

Rousey showed little defensive acumen as she staggered and stumbled backward with Nunes relentlessly pursuing her and landing 27 punches in the brief bout.

"Forget about Ronda Rousey!" Nunes shouted to the sellout crowd. "She's going to go do movies. Forget about her. She has a lot of money already."

Rousey's future in the sport is clearly in question, with retirement now clearly an option after her second loss in a row, following the defeat by Holly Holm last year.

"That's it for her," Nunes said. "For sure, she's going to retire."

Referee Herb Dean stopped the bout with Rousey still on her feet, and Rousey briefly protested the stoppage before leaving without giving an interview.

"Her coach put some crazy things in her head, and her career started going down," Nunes said. "I'm the real striker here."

Rousey could comfort herself with the fact she made a guaranteed $US3 million for her comeback bout, while Nunes' guaranteed payday was just $US200,000.

"I knew I was going to beat (Rousey)," Nunes said. "I'm the best on the planet."

Earlier, Cody Garbrandt won the men's bantamweight title, battering champion Dominick Cruz to earn a surprising decision victory.

Garbrandt remained unbeaten with a virtuoso performance to claim the belt held for the past 11 months by Cruz, who ended up with a gaping cut over his left eye.

Cruz hadn't lost an MMA fight since March 24, 2007, winning 13 straight bouts.