'The Notorious' was too slick for his opponent when the pair first met in 2014, claiming a stunning first-round knockout victory at UFC 178.
However, the tables were turned in their January rematch at UFC 257 in Abu Dhabi, with Poirier displaying a kickboxing masterclass to claim a second-round TKO victory and dash McGregor's already unlikely hopes of a rematch with the retired Khabib Nurmagomedov.
Now, the pair go head-to-head for a third and likely final time, with the winner then in line for a title shot against current lightweight champion Charles Oliveira, who won the strap with a second-round TKO of three-time Bellator champion Michael Chandler in May.
With the match-up now swiftly approaching, Sportsmail takes you through everything you need to know.Insurance Loans Mortgage Attorney Credit Lawyer
Dustin Poirier (left) and Conor McGregor (right) are set to complete their trilogy this weekend
Poirier claimed an emphatic stoppage victory in their rematch at UFC 257 back in January
The eagerly-anticipated match-up between McGregor and Poirier is scheduled to take place on Saturday, July 10 at the T-Mobile Arena in Las Vegas.
The pair are expected to walk to the ring at around 6am BST, though that of course will depend on results beforehand.
The main card will begin at 3am BST, with four fights to be completed before McGregor and Poirier take the octagon.
The preliminaries will run beforehand from 1am to 3am.How to watch the fight
As expected, the trilogy bout between McGregor and Poirier will be a pay-per-view event.
In the UK, fans will be able to watch the fight on BT Sport Box Office at a price of £19.95.Insurance Loans Mortgage Attorney Credit Lawyer
The preliminaries will be shown on BT Sport 2, available for subscribers to watch on the BT Sport website and app.
Sportsmail will also be running a live blog, so you can keep up-to-date with us.
Should you miss the fight, repeat showings will begin from 12pm on Sunday, July 11 and will be shown every three hours until midnight on Friday, July 16.How do their records compare?
The brutal defeat for McGregor was his third loss in six fights, while Poirier has lost just one in seven, against Khabib Nurmagomedov
Height: 5ft 9in
Record: 27W, 5L (1 no contest)
Last six fights: 5W, 1L
Height: 5ft 9in