I don’t think there really are any actual horror anime’s. The anime’s that I actually find scary are the ones where "horror" is not its primary focus. So one of the scariest anime’s I’ve ever seen was Monster.
And Mononoke and Ayakashi are Japanese horror / folk tale and are both good.
Instead of "horror", I think "psychological thriller" might be the better term? Given that ou mentioned Monster, which is more thriller than horror in my opinion. For horror, I'm thinking the works of Itou Junji, who is likely the most famous horror mangaka nowadays (though I don't claim to know the horror genre well). – Justin Wu7 years ago
If what you're going for is actually scary anime and not anime in a specific genre, maybe make a list of genuinely frightening anime and why they scare people even though they're not necessarily in the 'horror' genre. – Wolfstar967 years ago