The rivalry between the University of Southern California (USC) and the University of California, Los Angeles (UCLA) is one of the most fierce in college football - and that carried over into the stands where a fight broke out.
USC and UCLA met for the first time as Big Ten opponents in their annual Battle for the Victory Bell at the Rose Bowl in Pasadena over the weekend.
While the game itself was a close affair, it was an incident in the stands that has made the rounds on social media.
In a video posted to the r/PublicFreakout subreddit, a woman wearing a blue denim shirt and a UCLA bucket hat was seen smacking a man wearing a red shirt, the colors of USC.
It's unclear what happened prior to the video being recorded, but it captured the woman suddenly winding up and slapping the rival fan.
Those around her sounded shocked by her actions - with gasps and shouts of 'What the f***' being heard.
WARNING: VIDEO CONTAINS EXPLICIT LANGUAGE
This woman in a hat slapped the man wearing a red sweatshirt at a college football game
It isn't clear what happened next. No reports have surfaced of any fighting or arrests at the game.
DailyMail.com has reached out to the Rose Bowl for any comment on this matter.
As for the game itself, USC claimed victory over UCLA in a 19-13 win that makes them bowl eligible.
The Trojans of USC took a fourth-quarter lead with under seven minutes to go when quarterback Jayden Maiava completed a touchdown pass to go up 16-13. A field goal from kicker Michael Lantz from 30 yards out extended the lead.
The Bruins of UCLA fell to 4-7 on the season, confirming that they are ineligible for a bowl game. Their last game of the season is Saturday against Fresno State.