The medieval Icelandic undead are corporeal beings that haunt the literature produced on the remote North-Atlantic island between the thirteenth and fifteenth centuries. They often appear in the dark of winter, killing livestock and farmhands and threatening the survival of the community of the living. We encounter them across different genres, particularly in saga literature, and their appearance varies depending on this generic context. Scholarship has frequently attempted to categorize them, but this yields limited results. Other approaches, e.g., to the role they played for the medieval Icelandic elite who produced the sagas, have been more fruitful. Beyond medieval literature, the medieval Norse undead lead rich afterlives both in Scandinavian folklore, where they retain their corporeality but gain specificity, as well as in popular culture, where they can be creatively adapted to different contexts.