Phillip Phillips' mother Sheryl Phillips -- who appeared on several episodes of "American Idol" during Phillip's championship run last season -- was arrested for DUI earlier today, TMZ has learned.

Law enforcement officials tell us, an undercover unit observed Sheryl swerving her van across lanes of traffic in Albany, Georgia -- and pulled her over.

We're told ... based on what officers observed after the stop ... they had reason to believe Sheryl was under the influence of alcohol and/or drugs.