The central Middle Ages witnessed a remarkable upsurge in sources containing ethnic stereotypes. Should we interpret the increase in ethnic images as evidence that people identified more strongly with ethnic or national groups from the 12th century onwards? And to which extent was ethnic identity informed by cultural, religious, and medical discourses, as well as forged by political elites as part of a state-formation process? Addressing these questions from a broad range of perspectives and incorporating a wide body of research, this article offers a review of the scholarship on ethnic identity formation and the relevance of ethnic stereotyping in religious-eschatological thought, medical science, and political rhetoric from the 12th century. It challenges the notion that ethnic stereotyping reflected random expressions of hatred, or, conversely, expressions of nationalist patriotism in the later Middle Ages.