It's time ... to rumble!!!!!

UFC ring announcer Bruce Buffer says if Conor McGregor vs. Floyd Mayweather actually happens -- he'd love to do the fight with his famous ring announcer brother, Michael Buffer!!

Of course, you know Michael Buffer for famously busting out his signature catchphrase at some of the biggest boxing matches of all time ... "LET'S GET READY TO RUMBLE!"

So, if the two sports collide ... why not bring in the best from both sports to fire up the crowd??!