Georges St-Pierre, one of the greatest and most popular MMA fighters of all time, is expected to announce his retirement on Thursday at a news conference in Montreal.

RDS, a French-language sports network in Quebec, was first to report the news of St-Pierre’s decision to quit the sport he helped launch to widespread popularity.

CONFÉRENCE DE @GeorgesStPierre DEMAIN AU CENTRE BELL.



Selon les informations recueillies par RDS, il annoncera sa retraite. — Benoit Beaudoin (@BenBeaudoinRDS) February 20, 2019

St-Pierre, 37, was already a three-time UFC welterweight champion when he first retired on top following his ninth consecutive title defense in 2013. He returned to the octagon in November 2017 and defeated Michael Bisping to capture the UFC middleweight title, becoming only the fourth fighter in the organization’s history to win titles in more than one weight class.

The Québec native was a key figure in the sport’s mid-2000s ascent to the mainstream, headlining the largest UFC event in North American history when his title defense against Jake Shields in the main event of UFC 129 drew a sellout crowd of 55,724 to Toronto’s Rogers Centre.

St-Pierre, who is under contract with the UFC but hasn’t fought in more than 15 months, had been reportedly campaigning for a fight with Khabib Nurmagomedov, the organization’s lightweight champion.

Wednesday’s report prompted Nurmagomedov to offer up the fight in a post on Instagram, saying: “Let’s do it in November. After this fight you can retire.”

But St-Pierre, while expressing appreciation of Nurmagomedov’s offer, intimated to ESPN that his decision was final.

“I saw what Khabib wrote, and I appreciate it very much,” St-Pierre told the network. “Unfortunately, these decisions aren’t up to us. I will address everything at the press conference tomorrow.”