"Love & Hip Hop Atlanta" star Benzino's baby mama, Althea Eaton, went upside his head during an argument Sunday night ... according to cops who witnessed it, and quickly arrested Althea.
Law enforcement sources tell TMZ ... LAPD was called to Althea's home in the San Fernando Valley to check out a domestic dispute. We're told Althea wanted Benzino to get out, and he wasn't cooperating.
Responding officers tried to calm things down, but 'LHHA's' first couple of trouble didn't disappoint -- we're told Althea whacked Benzino in the head right in front of the cops. She was arrested and booked for misdemeanor battery.
Her bail was set at $20k, and we're told she bonded out early Monday morning.