Buddy Boy is a 1999 psychological thriller film written and directed by Mark Hanlon and starring Aidan Gillen, Emmanuelle Seigner and Susan Tyrrell. The film premiered at the 56th Venice International Film Festival.

Rex Reed of The New York Observer called it "a curious, unsettling, darkly conceived and absolutely fascinating little film. Not since Roman Polanski at the pinnacle of his European weirdness have I seen a film this strange and riveting."