McGregor, sources say, had verbally agreed to the fight weeks ago. He made it clear following his loss to Poirier earlier this year that he wanted to run it back with Poirier right away.
Poirier defeated McGregor in January via second-round TKO in a rematch of a 2014 fight. Back then, at UFC 178, McGregor defeated Poirier via first-round TKO.
The trilogy, which is expected to be one of the most lucrative in UFC history, is slated to serve as a five-round main event at 155 pounds, just like the rematch was. The original fight took place at 145 pounds.
McGregor (22-5) will be looking to secure his first win since January 2020, while Poirier (27-6, 1 NC) will hope to extend his winning streak to three in a row. The winner of this fight could very well be next in line for a lightweight title shot, though that stipulation hasn't been announced.
The location for the event hasn't been announced, but it is expected to be open to fans, sources say.