Ben Affleck's Massive Back Tattoo Is the REAL DEAL!!!

Ben Affleck is like a phoenix rising from the ashes ... or at least his back is.

Affleck was spotted on set this week with a giant tattoo on his back and most people figured it was just for the movie, but our sources say not only is the ink 100% real, it's actually been there for a while.

We actually got a glimpse of the artwork in July, but again ... everyone just assumed it was for a role. We're told the tatt was already a work in progress when things went south with Jennifer Garner.

Single Ben likes his ink.