Johnny Rotten Files Stalker Report Against Alleged Obsessed Fan

Punk rock legend Johnny Rotten says he has an obsessed stalker in his midst who's been hitting him up on his phone and even coming to his house.

Law enforcement tells TMZ ... the Sex Pistols singer told L.A. County Sheriff's deputies a fan started harassing him last month by dropping letters in Johnny's mailbox -- and he says she picked up the pace, FAST.

Johnny said the woman took it to the next level by trespassing onto his Los Angeles-area property and strolling around his backyard. He says he even came face-to-face with her, and told her to scram.

That's when Johnny claims he started getting phone calls from her -- and that's when he decided to file a stalking report with the sheriff's department, which is now investigating.