The former Ultimate Fighting Championship featherweight and lightweight champ first quit the sport in April 2016 with his now-famous tweet: "I have chose to retire young".
If his retirement is for real, he'll finish his career with a 22-4 overall record.
Posting the picture of himself and his mother, Conor McGregor failed to explain the rationale that made him to retire from fighting this time around. "What a ride it's been!"
There had been no shortage of speculation as to whom McGregor's next opponent could have been with Brazilian Anderson Silva among those who had been strongly tipped to face off against him.
McGregor's hand hadn't been raised in victory since November 2016, when he stopped lightweight Eddie Alvarez to become the first fighter in UFC history to hold two championship belts simultaneously.
How major U.S. stock indexes fared Friday
At the close in NYSE, the gained 3.15% to hit a new 3-months high, while the index added 2.62%, and the index climbed 2.06%. The S&P 500 and Dow Jones indexes are now down about 6 per cent and 9 per cent, respectively, from their all-time highs.
The controversial fighter, nicknamed "The Notorious", first announced his retirement from the sport in March previous year after being battered into submission by arch-rival Khabib Nurmagomedov in October 2018. "You know how Conor works".
The former UFC featherweight and lightweight champion said he was stepping away in 2016, and then he retired again in March 2019 after losing to Khabib Nurmagomedov at UFC 229 in October 2018.
Dana White, the president of UFC, commented on the tweet and said the announcement may have happened because of the pandemic.
"If that's what Conor is feeling right now - Jon Jones, Jorge Masvidal, I feel you".
McGregor gave no reason for his sudden retirement and whether his rationale falls in line with those of Jones and Masvidal. It's not like I'm going, 'Holy s***, this is insane, this is nuts'. "So, on a certain level, I totally understand it and get it".
He made a return to the octagon in January after 15 months of inaction to knock out American Donald "Cowboy" Cerrone in just 40 seconds in Las Vegas.