There are several horror films that claim to be based on true stories. 'The Exorcist' is one such example. It's said to be inspired by the real-life exorcism of a young boy. Another is 'The Texas Chainsaw Massacre', which has roots in real crime cases and urban legends.
Some well-known horror films based on true stories include 'The Conjuring' and 'The Amityville Horror'. These movies draw inspiration from real-life events and paranormal experiences.
Well, 'The Blair Witch Project' is often considered a horror film based on true events. It creates a sense of authenticity through its documentary-style approach. Also, 'A Nightmare on Elm Street' is rumored to have elements inspired by real nightmares and sleep disorders.