The 135-pound title fight will take place on a UFC 265 pay-per-view event in August. The event does not yet have an official date or location, but Aug. 7 is the current target.
Nunes (21-4) is widely considered to be the greatest female fighter of all time. She captured the UFC's bantamweight title in July 2016 and has successfully defended it five times. She became a two-weight champ in December 2018, knocking out Cris "Cyborg" Justino for the 145-pound featherweight title. She has defended that belt twice.
Born in Brazil and now fighting out of South Florida, Nunes hasn't fought at 135 pounds since a title defense against Germaine de Randamie in December 2019. She fought just once in 2020 and most recently in March of this year. Both of those title fights were contested at 145 pounds.
Nunes, 32, hinted at a fight in a social media post on Thursday. "There's something new coming," Nunes wrote in Portuguese. "Let's go to the next."
Pena (10-4) has aggressively campaigned for a shot against Nunes since her victory over Sara McMann at UFC 257 in January. The Chicago-based contender has gone so far as to accuse Nunes of avoiding her. Pena is a former winner of "The Ultimate Fighter" reality series and holds a 6-2 record in the UFC. Her only losses have come against current or former UFC champions, in de Randamie and Valentina Shevchenko.
"I'm excited, pumped and ready to go," Pena told ESPN. "This opportunity at a UFC title is what I've wanted in this sport all along."