Troy Polamalu THE PROOF HEAD-SHAVING VID WAS HOAX

His teammates appeared to have pulled the classic Jackass head-shave prank on his million-dollar hair -- but Pittsburgh Steelers wrecking ball Troy Polamalu tells TMZ, it was all FAKE ... his locks are still intact.

BONUS: Troy also drops a serious hint about what team he'll sign with once his contract expires next year ... watch the clip!