Amanda Bynes was arrested for DUI in West Hollywood early this morning .
Law enforcement sources tell us, Bynes was attempting to pass a cop car in her black BMW ... when she sideswiped the right rear panel of the vehicle. She was pulled over and cops determined she was not fit to be behind the wheel.
We're told the 26-year-old actress was busted at 3 AM ... she's still behind bars.
According to her booking sheet, Bynes is 5'7" and 125 lbs. Her bail has been set at $5,000.
Bynes has been frequenting the Hollywood party scene recently, hitting up several clubs over the last few weeks.