Both sides have verbally agreed to the bantamweight championship, and the pay-per-view event will take place at T-Mobile Arena in Las Vegas, sources told ESPN.
UFC officials have not confirmed the bout's official placement on the card.
Nunes (18-4) is the current champion of the 135- and 145-pound weight classes. She is coming off the fourth defense of her bantamweight title in July, a head kick knockout of Holly Holm at UFC 239.
Originally from Brazil, now fighting out of American Top Team in Coconut Creek, Florida, Nunes is ranked as the No. 1 pound-for-pound fighter in the world by ESPN.
De Randamie (9-3), of the Netherlands, is a former featherweight champion. She won the 145-pound belt in February 2017 by defeating Holm. However, she was stripped of the belt later that year when she refused to face No. 1 contender Cris "Cyborg" Justino over concerns of prior use of performance-enhancing drugs.