Brazil's Amanda Nunes stunned the mixed martial arts world with a first-round submission win over Miesha Tate to claim the women's bantamweight title at the UFC 200 event in Las Vegas.

Despite its brevity, the fight at the sold-out T-Mobile Arena easily lived up to its billing as the main event.

Tate was rocked early by punches from strike specialist Nunes, who switched her attention to submission attempts when the fight went to the mat and quickly finished Tate with a rear naked choke after 3:16 of the first round.

It was the same submission Tate used to claim the title from Holly Holm in March, and the belt has now changed hands three times in nine months since Holm beat Ronda Rousey.

"Oh my God, 10 years of my life working for this moment! I feel amazing!" an elated Nunes said after being presented with the belt.

In the other title fight on the card, Nunes' fellow Brazilian Jose Aldo took a step closer to reclaiming the featherweight title he lost to Conor McGregor at UFC 192 by beating Frankie Edgar in an unanimous decision.

Having been stopped by McGregor in just 13 seconds last December, the fleet-footed Aldo put on a clinical display of counter-punching to outpoint the aggressive but ineffective Edgar to claim the interim title.

The defeat put an end to Edgar's five-fight win streak that stretches back to his previous defeat to Aldo in February 2013, which also was a unanimous decision.

"Frankie's a great guy and I respect him, but I have one goal and that's to beat this guy (McGregor)," Aldo said.

McGregor is due to face Nate Diaz, who he lost to in March, in a welterweight bout on Aug. 20 and after that he is expected to drop down two weight classes to meet Aldo.

The bout between Tate and Nunes was elevated after a positive doping test saw light heavyweight Jon Jones withdraw from his title fight against champion Daniel Cormier.

Cormier was instead pitted against former middleweight champ Anderson Silva, widely regarded as one of the greatest fighters in the sport, who stepped in with two days' notice.

Former Olympic wrestler Cormier wasted no time taking the fight to the mat where he utilised his skills to dominate his 41-year-old Brazilian opponent on the way to a comfortable victory on the scorecards.

Popular former UFC heavyweight champion and current WWE wrestler Brock Lesnar returned to the octagon after a four-year absence to defeat Mark Hunt after three tough rounds.

In the other heavyweight bout on the card, Cain Velasquez scored a TKO victory over Travis Brown, the referee calling a halt with just three seconds left in the first round.

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