A woman is so infatuated with John Cusack, she showed up at his house multiple times, and even threatened to do a little "black" magic on his boners ... according to the actor.
Cusack filed docs requesting a restraining order against Marieretno Subali ... who he says showed up at his house, uninvited, 3 months in a row -- but John was never home.
Cusack believes the woman is monitoring his travel through social media, and fears she'll be waiting for him one day when he gets home.
He says Subali's reached out to his family as well ... sending a couple of creepy emails to his sister-in-law. In one, she says Cusack came to her in a dream, and called him her favorite actor from the movie, "Serendipity."
Another email was much darker -- in it, he says Subali threatened to perform a "black candle spell on him," which, according to her, would make him impotent ... for life.
That was enough for a judge to grant Cusack the restraining order. Subali has to stay 100 yards away and have no contact with Cusack, as well as his brother and sis-in-law.