Gene Hackman pimp-slapped a homeless man who physically threatened the actor and his wife outside a New Mexico restaurant ... TMZ has learned.
Law enforcement sources tell TMZ ... the incident went down Tuesday as Hackman and his wife were leaving a Santa Fe restaurant. We're told a homeless guy named Bruce Becker approached them in a threatening manner.
We're told the incident escalated big time when Becker called Hackman's wife a "c**t" -- and then Hackman dished out some street justice ... slapping Becker across the face.
Becker then called the cops to report the incident.
We're told cops interviewed Hackman and his wife, determined the slap was in self-defense ... and, for now, no charges have been filed.