Josh Hartnett’s diving into scary moments in his past …

revealing he left Hollywood because he was being stalked — including by a man he says once arrived at his location with a gun.

The actor spoke with The Guardian via Zoom from his estate in Hampshire, England …

a sprawling countryside where he lives with his wife partly because living in L.A. started to feel too dangerous.

JH says it’s not the only reason he left L.A. about 20 years ago … but, it didn’t help that people started showing up at his house.

Hartnett says these were straight-up stalking incidents … adding that a man once “showed up at one of my premieres with a gun, claiming to be my father. He ended up in prison.”

Basically, Hartnett worried he’d get crushed by fame … and decided to change his life before Hollywood could end it.

Obviously Hartnett still makes movies … including M. Night Shyamalan’s “Trap” — a psychological horror-thriller coming out this week where he plays a serial killer who has to escape a stadium-wide police operation, a perfect role for getting in the mind of his own stalkers.

Hartnett says his career trajectory’s just fine with him FWIW … adding he spends a ton of time with his kids he otherwise probably wouldn’t have.

That said, it seems his career could’ve gone way differently … but, H’wood itself made the man feel trapped.