Taco Bell Cantina Security Guard Slaps Woman on Video

A security guard at a Taco Bell slapped a woman clean across the face as she tried to place an order ... and it's all on video.

Footage from inside the Taco Bell Cantina location in downtown Los Angeles shows the restaurant's security guard confronting a woman and smacking her upside the head.

The video picks up with the woman beelining to order from a kiosk ... and the guard is hot on her heels. He grabs her arm, turns her so they're face to face and unloads a vicious slap.

The woman walks away and the guard follows ... she tells him to get away and he tells her to leave the premises.

Customers in the store mostly watch in stunned silence ... and the woman argues with the security guard before he's ultimately able to usher her out the front door.

Unclear what sparked the confrontation ... the video does not show the buildup.