In 1999, Daniel Myrick and Eduardo Sánchez’ found-footage horror film The Blair Witch Project was released alongside a widely successful marketing campaign that made the world believe that three film students had disappeared in the Maryland woods. The campaign is often remembered as an internet sensation, a hoax, or simply a viral marketing campaign, while few consider its gamified components, or particularly its likeness to an alternate reality game (ARG). ARGs are collaborative, transmedia games which blur the boundaries between fact and fiction and hide their own game-ness through immersive puzzles, compelling mysteries and vast story-worlds. This thesis therefore offers a reading of The Blair Witch Project campaign through the lens of an ARG. More acutely, this thesis explores ARG-like marketing techniques, specifically within the horror genre, positioning Blair Witch as a trailblazer for other film-based ARGs and ARG-type techniques. The first chapter of this thesis formulates an ARG axis model, which is then used in the second chapter to reconsider Blair Witch through the framework of an ARG. The third chapter of this thesis showcases other horror film examples through this same ARG model, including Cloverfield (Matt Reeves, 2008) and Unfriended (Levan Gabriadze, 2014) among newer examples, establishing the Blair Witch phenomenon as a contemporary trend within the genre. Finally, I consider how and why these novel industrial tactics work so well within the horror genre in particular, as they offer new modes of engagement and horror creation in the digital era.