Matthew McConaughey learned fame has its perks ... but apparently Jennifer Lopez's fame has even better ones.

The actor revealed on Thursday's episode of Josh Horowitz's "Happy Sad Confused" podcast that name-dropping JLo once got him out of a "major, major mess" during a late-night police stop in Mexico.

Matthew says he was driving a nice truck way down south when officers pulled him over ... and he quickly realized the "gringo" behind the wheel had caught their attention.

He started reaching for his wallet as the situation heated up ... but then tried a different form of identification -- his JLo connection!

Matthew asked the officers if they knew Jennifer and had seen their 2001 rom-com, "The Wedding Planner" ... before proudly informing them, "Yeah, yeah, it was me."

Just like that ... the traffic stop turned into a meet-and-greet ... with the officers snapping photos with Matthew before sending him on his merry way.

No ticket, no trouble, just a few selfies ... alright, alright, alright!