Christina Milian -- Bodyguard Swats Woman in the Face [VIDEO]

EXCLUSIVE

Christina Milian was caught in the middle of some Hollywood nightclub violence Sunday night -- after a woman (wearing only a bra and shorts) went after Christina's bodyguard ... and the bodyguard swatted her away with an open palm to the face.

We have no idea who the woman is or why she was upset -- but the video's intense.

Christina was in a great mood on her way into Hooray Henry's ... but the short-tempered security guard definitely led her out in a hurry. Check the clip.