The Norse werewolf is a joint term under which the author has chosen to subsume the diversity of motives based on or containing elements of lupine therianthropy within the Old Norse literary corpus. The purpose of the study is to identify and explicate the underlying structures behind the Norse werewolf motif using an interdisciplinary approach with an emphasis on psychology, anthropology and history of religion. The author argues that the werewolf figure, in all of its various literary manifestations, should be interpreted as a marginal entity that, serving as a reflection of the Other, acts as a transformative principle conveyed in the texts through Fenrir and other lycomorphous mythological creatures, the stories of Norse outlawry, the berserker motif and the appearance of werewolves in Medieval Icelandic romances. The thesis concludes with the idea that the werewolf is a decoding vehicle within Norse culture s multilevel quest for identity.