Paris Jackson's alleged stalker is now behind bars after cops say he showed up at her home earlier this month ... and we're told that may not have been his first visit.
Law enforcement tells TMZ ... 37-year-old Ruben Polanco was arrested September 4, when he showed up at Paris' L.A.-area home. We're told she had security there which kept him at bay until cops came and took him away.
The L.A. City Attorney's Office has now charged him with 4 misdemeanors -- including stalking and prowling. He's currently sitting in jail on $20,000 bail ... as the LAPD Threat Management team continues to investigate.
Cops say Polanco has a history of ending up at Paris' place -- he allegedly was on her property New Year's Day, and officers say he returned 2 times in August, in addition to the most recent incident in September.
TMZ broke the story, police were called to her home in August for an alleged intruder hanging around her backyard. We're told the model and singer wasn't home at the time, but a friend called the cops when he was seen on the property.