MONTREAL — Canada's Georges St-Pierre said Thursday that he's leaving mixed martial arts at the top of his game, expressing few regrets as he formally announced his exit from the sport.

The 37-year-old from St-Isidore, Que., appeared serene as he explained his decision at a news conference at Montreal's Bell Centre.

"There's no tears. I'm very happy to do it," he said.

"It takes a lot of discipline though to retire on top. It was a long process in my mind, but it's time to do it .... I always said that I want to retire on my own and not be told to retire."

St-Pierre, a two-division champion, leaves with a record of 26-2-0 and a 13-fight winning streak. He holds the record for most 170-pound title defences at nine.

His departure was precipitated in part by the UFC's reluctance to grant St-Pierre a high-profile fight with lightweight champion Khabib Nurmagomedov. While the Russian fighter appeared eager, tweeting that it would be "an honour" to fight the Canadian in November, St-Pierre said Thursday that "the UFC has other plans."

However, the retiring athlete said he understood the UFC's desire to promote fighters who are willing to commit to several future bouts.

"I would go fight one fight at a time, but it's a bit selfish on my part, because this business isn't about that," he said. "It's about what's next."

And while he expressed some disappointment that the fight didn't materialize, he also acknowledged that he no longer has the same motivation he did when he was younger. The stress of fighting, risk of injury and threat of humiliation or defeat all took a toll, he said.

"I'll tell you the truth. Fighting, fighting — I don't really like that," he said.

"I have never had a moment of pleasure the day of a fight. I hate it to death. However, I love the freedom it gives me, I love the work and the feeling of camaraderie with my colleagues, and the feeling of victory when you succeed is indescribable."

St-Pierre debuted on the big stage with a unanimous decision win over Karo Parisyan at UFC 46 in 2004. He won his first welterweight championship via knockout over Matt Hughes at UFC 65 in 2006.

After losing the title to Matt Serra, he recaptured the belt in 2008 via TKO in their rematch at UFC 83 in Montreal.

St-Pierre gave up the 185-pound crown a month later, citing his ulcerative colitis. Despite that limited activity, he still stands eighth in the UFC's pound-for-pound rankings.

St-Pierre said consideration for his health, both physical and mental, played a part in his decision to retire. While not overly concerned about "kicks to the head," he said the intense stress of preparing for fights contributed to his health issues.

"It takes a lot out of me. It takes a lot of energy, a lot of stress, creates a lot of anxiety. And stress and anxiety, for me, is probably what caused the problem I have," he said referring to the colitis.

"Every time I went in training camp, I'd have a hard time sleeping, thinking scenarios in my head .... It's a crazy lifestyle," he said moments later.

In 2011, St-Pierre set the largest UFC gate outside the U.S. at US$12.075 million when he headlined UFC 129 at the Rogers Centre in Toronto. The event had the second largest attendance in UFC history with 55,724 fans.

St-Pierre won Sports Illustrated fighter of the year in 2009. He was nominated for best fighter at the ESPY Awards in 2008, 2010, 2011 and 2018.

He said he hasn't yet decided what to do in retirement, other than taking a vacation "somewhere warm and exotic" and continuing to train.

"For me, it's just au revoir. It's just goodbye. I'm not dead. I'm always going to be training. I see a lot of athletes when they retire, they become fat and out of shape," he said. "It ain't going to happen to me."

And while he said he's happy to retire, he didn't fully rule out a comeback if the right offer were to come along.

"If I feel tempted, maybe I'll come back, but for me it's over for the moment," he said.