Charlamagne Tha God -- Earning Respek With His Fists ... Sparring With Boxing Star (VIDEO)

Charlamagne Tha God let former boxing champ Shawn Porter do something rappers have wanted to do to Charlamagne for years ... punch him in the face ... in a live sparring match in NYC yesterday.

It all went down at Gleason's boxing gym on Wednesday afternoon ... and we're told the whole thing was the idea of Shawn's dad and trainer, Kenny, who's pretty good friends with Mr. Tha God.

Check out the clip -- Charlamagne isn't exactly Sugar Ray Robinson in there, but gets in enough good shots to not look like a newbie.

BTW -- Porter is training for a huge title fight against Keith Thurman later this month ... by fighting a guy who sits down for a living.