Lady Gaga's Bodyguard -- FEROCIOUS Takedown in Romania

Lady Gaga's bodyguard WRECKED some dumbass autograph seeker who tried to get too close to the singer in Romania ... and the brutal takedown was all caught on tape.

Gaga was trying to walk through her hotel, flanked by two beastly private security guards, when the autograph seeker tried to go through a revolving door and get in Gaga's face.

But the bodyguard POUNCED ... grabbing the dude by the head and slamming him to the ground ... instantly neutralizing the threat.

Gaga seemed startled at first ... but quickly realized she was in good hands.