The American landed a flurry of head punches on McGregor for an incredible victory in Abu Dhabi.
Fighting for the first time in 12 months, McGregor had made a decent start before Poirier responded with several blows for the knockout.
In what was a rematch of their fight from 2014, when McGregor was victorious, Poirier delivered a stunning result to gain some revenge.
WHERE WAS THE FIGHT WON?
Poirier landed a huge left hand that rattled McGregor in the second round. He backed that up with several shots that sent the Irishman to the canvas, ending the fight.
WHAT DOES IT MEAN?
Will Khabib Nurmagomedov (29-0) come out of retirement? Poirier claimed he was the champion after his win over McGregor, if Khabib was not returning, but the American should be lining up a shot at the UFC lightweight holder.
THEY SAID WHAT?
"I'm happy but I'm not surprised. I put in the work. Conor took this result very professionally, he's a pro and nothing but respect. We're 1-1, maybe we have to do it again," Poirier said after his win.
NEW RECORDS (W-L-D):
REST OF THE CARD
Michael Chandler made quite the impression on his UFC debut. He made quick work of Dan Hooker with a first-round knockout.