MMA superstar Conor McGregor has obtained a professional boxing licence to further fuel rumours he will switch disciplines to seek a fight with Floyd Mayweather Jr.

McGregor was issued with a licence by the state of California on Wednesday, meaning speculation surrounding the outspoken Irishman and undefeated pound-for-pound boxing great Mayweather is unlikely to relent.

"He got a licence today and a federal ID," California State Athletic Commission executive officer Andy Foster told MMAFighting.com. "He's a California boxer now.

"He's qualified. I'd love to see him fight in California. It just needs to be the right opponent. Certainly a high-level opponent. We're happy to license him. We're happy he's a California fighter."

McGregor, 28, is the current UFC lightweight champion and former UFC featherweight champion, a title stripped from him on Monday. Mayweather, 39, says he's "happily retired" after going 49-0 over his career while winning championships in five weight classes.

McGregor, who is 21-3 as an MMA fighter after his lightweight-title win over Eddie Alvarez earlier this month, and Mayweather have teased a potential fight since McGregor tweeted a mock poster in May.

The two have publicly thrown barbs at each other through the media since.

On Tuesday, McGregor's coach John Kavanagh told The Sun that talks between the two camps had taken place.

“If the odds were good enough, I’d put a few quid on (the fight happening) next year," he said.

“I’m not breaking any news saying that there’s conversations going back and forth for the last year or so.

“Is it getting any close? I don’t know, but it certainly wouldn’t surprise me that it’s going to happen.”