Floyd Mayweather's camp has a message for Manny Pacquiao -- enjoy your "Mayweather" punching bag while you can ... 'cause it's the ONLY way you're gonna beat up on Floyd's face.
The bag was a gift from boxing super fan and legendary attorney Robert Shapiro (from O.J. Simpson fame) ... who commissioned the piece from a popular artist.
We spoke with a bunch of guys from The Money Team who tell us Floyd got a good laugh out of the bag -- but made one thing clear, it's only fueling Floyd's anti-Pacquiao fire.
As for the artist ... Gena Milanesi tells TMZ Sports the bag's not just for show -- the artwork has been coated with a special varnish so it can take whatever beating.