Jenna Jameson's bday celebrations got off to a rocky start -- the XXX star was arrested for battery Saturday night ... before her shindig even kicked off.
Law enforcement sources tells us ... Jameson was hanging out in the Balboa Peninsula neighborhood of Newport Beach around 8 pm ... when she allegedly battered someone.
We're told the alleged victim put Jameson under citizen's arrest and then flagged down a police officer. The cop arrived and cited Jenna for battery. She was later released.
Jenna was supposed to attend an early birthday party at Heat Ultra Lounge in Anaheim later that night (real bday is April 9). No word if she made it or not.
Jenna's no stranger to handcuffs ... she was arrested for a DUI last year, after crashing her car into a light pole.