This is a historical and anthropological study of the myth of the werewolf aimed at reflecting on the metamorphoses of evil and understanding the long evolution of a mythical structure. Legends and folklore allow us to explore the brutal bestiality of a figure loaded with sexuality, eroticism, and desire. From ancient times to the present day, the tragic narrative universe of a strange and dangerous wild world is unfolded, with elements of tenderness, that has contributed to defining the profile of civilization as its opposite. The myth was contaminated with religious fanaticism when werewolves were persecuted and burned during the times of the witch hunts. Roger Bartra is a Mexican and Catalan anthropologist and sociologist. He works as a research fellow at the University of Mexico (UNAM).