The UFC star, 33, was pictured behind the handlebars of a bike while enjoying a seaside cycle ride.
McGregor posted the picture to his Twitter account, tagging to world famous film star, politician and former bodybuilder Schwarzenegger as he flexed his muscles.
The Notorious captioned the snap: “What’s up, @Schwarzenegger!”
McGregor has piled on the muscle in recent months and years, and now looks completely unrecognisable to his featherweight days in the UFC.
Schwarzenegger himself has been no stranger to showing off his ripped body over the years.
McGregor knows the 74-year-old well, having previously worked with his girlfriend Heather Milligan.
Milligan is a renowned physio, and has helped McGregor in his rehab after suffering a horror broken leg in his last UFC bout against Dustin Poirier last July.
She also helped him recover from a torn ACL back in 2013.
Schwarzenegger and Milligan first got together that very same year, after they were spotted kissing in Santa Monica.
McGregor is eyeing a return to the octagon this year after spending an extended period out of action following his leg break.
He announced: “I am back,” on social media yesterday, with the Irishman having started boxing training again as he continues on his road to recovery.
McGregor is currently on a two-fight losing streak but teased a fight with lightweight champion Charles Oliveira for when he returns.