Law enforcement sources tell TMZ ... Marie Avgeropoulos -- who stars as Octavia Blake on CW's hit sci-fi show, "The 100" -- was arrested in L.A. last week and booked for felony domestic violence.

We're told a man called police very early on August 5 from inside a car ... claiming his girlfriend had hit him during a verbal argument. Sources say when police arrived, the man had marks on his body ... so Marie was taken to jail.

Her mugshot's just as edgy as her character on '100' -- albeit with a lot less blood and war paint on her face. She does appear to have been crying though.

A source close to Marie claims the actress was on new meds and mixed it with wine during dinner that evening ... which resulted in a bad reaction. We're told her boyfriend called police thinking they'd diffuse the situation rather than arrest her -- as they're both Canadian and unfamiliar with what'll get a person hauled off to jail in the U.S.

Our source says he begged cops not to take her away ... and even bailed her out after. Marie was released on $50,000 bond.