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.