Wikipedia indicates that Georges Melies’s *Le Manoir du diable* is considered the earliest horror movie, as noted in August 2011. It's true it’s just a short—roughly three minutes—but film was scarce back then, so I count it as a full-fledged movie. The storyline is simple: a protagonist experiences torment from demonic figures within an elaborate castle chamber. However, that wasn’t the reason people flocked to see these films. The appeal stemmed from witnessing movement on screen. I recommend seeing *Hugo*; it's remarkable and answered many questions I had about early cinema. It does a great job establishing the atmosphere. The film has noticeable Christian themes and concludes with Christianity triumphing over what are described as “tides of darkness.” A link to view this pioneering horror film is provided below. The movie employs very primitive special effects, relying heavily on smoke, mirrors, and fast editing. Because it’s so brief, judging the acting feels unnecessary; I'm simply amazed that this is a film over a century old—that’s incredible.

Source on TMDB