Bad news for Conor McGregor ... Floyd Mayweather's changed his mind about an MMA fight -- telling TMZ Sports he's way too busy to take a fight in the Octagon any time soon.
"I'm not thinking about fighting right now," Floyd told us while shopping with his crew in Beverly Hills.
Remember, Floyd was flirting with the idea of taking an MMA fight in 2018 -- with his eyes on McGregor -- and even reached out to UFC champ Tyron Woodley to set up a training program.
But Floyd says life has gotten in the way ... and he's been spending way too much time focusing on his family and growing his real estate business.
In fact, Floyd says he's a MAJOR investor in One Vanderbilt -- which he says will be the tallest skyscraper in New York.
Floyd says he's got more than $100,000,000 invested in NYC real estate projects -- and that's more important to him right now than learning a new combat sport.
The good news ... Floyd isn't completely closing the door on MMA, and insists he's keeping himself in shape just in case.
Stay tuned ...