The fight will complete a trilogy for Poirier and McGregor, as they previously clashed at UFC 178 in 2014 and at UFC 257 in January.
McGregor won the first fight by first-round technical knockout, and Poirier bounced back with an upset win in the second meeting via second-round TKO.
The 32-year-old Poirier has been on a roll as of late, winning six of his past seven bouts and running his career record to 27-6 with one no-contest.
Poirier's only loss during that stretch was a third-round submission at the hands of then-UFC lightweight champion Khabib Nurmagomedov, who has since retired.
Among the fighters Poirier has beaten besides McGregor are Justin Gaethje, Anthony Pettis, Eddie Alvarez, Max Holloway and Dan Hooker.
Meanwhile, McGregor has not been as active, fighting just three times since his three-fight year in 2016.
McGregor lost to Khabib by fourth-round submission at UFC 229 in 2018 and then returned from retirement to beat Donald "Cowboy" Cerrone by first-round TKO at UFC 246 last year before his loss to Poirier.
All told, the 32-year-old McGregor is 22-5 in his career and has held both the UFC lightweight and featherweight titles.
The July 10 fight between McGregor and Poirier will be big not only because it's their rubber match but also because of the potential title implications.
At UFC 262 on May 15, Charles Oliveira and Michael Chandler will fight for the UFC lightweight title vacated by Khabib.
Given the hierarchy of the 155-pound division, it stands to reason that the winner of Oliveira vs. Chandler could go on to face the winner of Poirier vs. McGregor with the UFC lightweight championship on the line.