Usain Bolt says Cristiano Ronaldo would "for sure" beat him in a foot race if the two decided to hit the track ... and yeah, he's dead serious.
The 8-time gold medalist was doing an interview with Spanish news outlet Marca over the weekend ... when he was asked straight-up -- who wins in a race RIGHT NOW??
"For sure Cristiano Ronaldo," the 34-year-old Jamaican legend says. "For me, he works out every day. He's a super athlete, you know what I mean?"
"He's always on top of his game.