Matthew McConaughey -- PUMPS UP TEXAS FOOTBALL TEAM ... 'Wolf of Wall Street' Chest Thump

Matthew McConaughey crashed the University of Texas football practice this week -- and tried to pump the guys up with the CHEST THUMP from "The Wolf Of Wall Street."

Head Coach Charlie Strong invited Matt to practice -- since he's one of the Longhorns' most famous fans -- and with the team all gathered around, the Oscar winner did his best Vince Lombardi.

"Ask yourself, Why do I play this game?" McConaughey said ... "I've found that when I've done my best work as an actor, it was only when I pushed myself to be better than I even thought."

Matt took questions from the team ... (someone asked him about his favorite movie he ever made) ... and then he led the guys in the famous W.O.W.S. chest thump.

He also explains how he came up with the chest thump ... and why he decided to use it with that other actor from the "Wolf" scene ... some guy named Leonardo DiCaprio.