Cam Newton's off-season is LITTTT!!!! ... 'cause the Carolina Panthers QB celebrated his new sneaker release by spittin' bars with 2 Chainz!!

Cam grabbed the mic and put his rap skills to the test while goin' bar-for-bar with Tity Boi to perform "Riverdale Road" at the Under Armour event Thursday  ... and we gotta admit, the dude's pretty impressive.

It shouldn't come as a surprise that the Pro Bowler decided to rock a Mad Hatter-esque look for the event ... 'cause Cam's known for makin' fashion statements. But the rapping's a pleasant surprise.

Maybe we'll get a 2 Chainz x Cam Newton collab soon??