This doctoral thesis complements earlier scholarship by Marina Warner concerning the Boogeyman as a figure representative of monstrosity and otherness by assessing these topics through an interdisciplinary lens. Employing a methodological approach that incorporates research from the fields of psychology, philosophy, and film studies, I analyse the Boogeyman within the context of the traditional fairytale and the modern horror film, and thereby reveal the key facets of this figure in the Western cultural imaginary. Specifically, I demonstrate that the villains of the contemporary slasher film (a subgenre of the horror film) are cinematic manifestations of the folkloric Boogeyman through a comparison of their physical and psychological attributes. Examining the archetypal properties of these characters, I argue that the traits that characterize the Boogeyman are the result of the fact that he is a composite of three archetypal forms: the collective Shadow, the Terrible Father, and the Death-Demon. I address three key questions: (1) what particular physical and psychological qualities are associated with the Boogeyman; (2) how the persona of the Boogeyman is constituted in the public consciousness; and (3) what moral, philosophical, and psychological role does he serve in Western culture. Over the course of this thesis, I demonstrate the fact that the Boogeyman represents the amalgamation of three archetypal components. Firstly, he embodies the role of the collective Shadow and functions to personify violent and anarchic characteristics that are repressed by the community and projected onto monstrous figures in the popular consciousness. Secondly, he is a manifestation of the negative attributes associated with the archetypal Father (referred to in literature as the "Terrible Father") who punishes individuals that defy hegemonic values. Finally, he is a cultural embodiment of the Death-Demon, a conceptual figure that personifies anxieties related to death, and the degeneration of the body. This thesis provides a comparative analysis of a series of case studies that clearly illustrate the characteristics synonymous with the Boogeyman in the Western cultural imaginary. I begin with an examination of Bluebeard, a homicidal villain featured in Charles Perrault's 1697 collection of fairytales titled Histoires ou contes du temps passé. In her seminal text No Go the Bogeyman, Warner posits Bluebeard as a clear example of the folkloric Boogeyman due to the fact that he is physically grotesque and morally repugnant. In Perrault's story, Bluebeard is a villain who marries and then murders a series of women for disobeying him, and subsequently stores their bodies in his private chamber. Extrapolating the salient characteristics of Bluebeard as the folkloric Boogeyman, I assess these traits under an archetypal lens and demonstrate that Bluebeard/the folkloric Boogeyman is a manifestation of the collective Shadow, the Terrible Father, and the Death-Demon. After determining the archetypal properties of the folkloric Boogeyman, I highlight the presence of these same qualities in popular villains from the contemporary American slasher films of the 1970s and '80s. Specifically, these characters include Michael Myers from Halloween (1978), Jason Voorhees of Friday the 13th (1980), and Freddy Krueger featured in A Nightmare on Elm Street (1984). Through my analysis of these terrifying figures, I situate them within a larger archetypal context of monstrosity and simultaneously establish their role as cinematic manifestations of the folkloric Boogeyman. This examination reveals the placement of the Boogeyman within the cultural imaginary as a violent disciplinarian who reinforces moral boundaries through sadistic acts of violence and paradoxically brings both chaos and harmony to the collective by preserving social borders. By extension, I demonstrate the link between the slasher film and the fairytale, both of which serve a didactic function, imparting hegemonic values to the public concerning sexual politics, social propriety, and moderation.