At its height, the Ottoman state ruled over a dizzying array of linguistic, religious and ethnic groups. In order to effectively rule over all these groups, the Ottomans had to develop some understanding of them. This paper will focus specifically on how the Ottomans understood and catalogued the different ethnic groups, both those well within state boundaries but also those adjacent to state boundaries. It will examine early modern Ottoman proto-ethnology registers, their relation to physiognomy, and the significance of such knowledge in the early modern Ottoman world. A keen awareness and study of ethno-racial human collectives (ejnas ve ?avayif-i nas) was an integral part of Ottoman socio-political discourse. During the early modern period, this Ottoman proto-ethnology was subsumed under the occult science of physiognomy (ilm-i firaset) as one of its methods (?uruk). At the root of physiognomy is the claim that a predictable correlation between corporeal signs and character traits can be deduced. This same logic was extended beyond individuals to human collectives, such as ethnic groups (jins or ta’ife), to claim that a set of predictable character traits could be discerned on the basis of ethnic background. The claim to predictability lent support to physiognomy’s scientific claim – an experiment that would reproduce the same results – and by extension to its proto-ethnological method. The systematized study of “ethnic” groups (jins or ta’ife), imbued with the scientific claims of physiognomy, had significant political ramifications within the context of the Ottoman state. The Ottoman notion of justice, which was conceptually rooted in equity (as opposed to equality), was keenly interested in knowing the predictable character traits of its constituent “ethnic” groups. On the basis of that knowledge, the most suitable functions for each group within the imperial configuration could be determined. In the Ottoman (as well as pre-Ottoman) ethics or akhlaq texts, this proto-ethnology was apportioned to household management. Large households – beginning with the imperial household itself – were major socio-political institutions in the Ottoman world, which were made up of numerous components, not least of which were slaves, servants and clients. On a household basis, it was absolutely crucial to know who would be suited to what function. And physiognomical proto-ethnology provided an apt shorthand for making such decisions.