UFC 264 will feature a Conor McGregor v Dustin Poirier main event and another rarity in sports - a capacity crowd.
The July 11 (NZ time) event has been made official, with the UFC announcing the Las Vegas event can sell tickets to capacity.
From May 2, Nevada will drop many coronavirus-related restrictions with another benchmark on June 2, although the statewide mask mandate is to remain in place.
"I'm so happy to finally be able to say Vegas is back," UFC president Dana White says in a tweeted video.
"This summer, Las Vegas is back open for business and on July 10, UFC 264, will be at the T-Mobile Arena in Las Vegas at 100 percent capacity. Ladies and gentlemen, that's 20,000 fans."
The bout will complete a trilogy of fights between the two. McGregor beat Poirier by first-round technical knockout in 2014, before Poirier got his revenge with a second-round TKO in their rematch at UFC 257 in January.
Earlier this week, the bout seemed at risk, as a Twitter spat erupted between the two fighters, with Poirier accusing McGregor of not following through with the charity donation he'd promised after their previous fight.
But McGregor signed the bout agreement against Poirier on Thursday morning, he has told ESPN. Poirier (27-6) officially signed earlier this week.
McGregor (22-5) reportedly agreed to the fight weeks ago. McGregor, 32, previously said he wanted another shot at the 32-year-old Louisiana native, after the Januray defeat at Abu Dhabi.