This dissertation considers the role that court dress played in the formation of Mongol cultural and political identity in the thirteenth and fourteenth centuries. By defining and analyzing the fashion system of the Mongol court principally in Yuan China, but also in Ilkhanid Iran, it demonstrates how the Mongols were able to manipulate symbols and ceremonies effectively via costume in the formation of their empire. Most art historical studies of the Yuan dynasty have focused on painting by Han Chinese “exiled” painters, ignoring Mongol contributions to the art and material culture of the dynasty. This dissertation initiates an understanding of the particular aesthetics of the Yuan dynasty, which incorporated diverse cultural traditions through textiles and dress. In addition, as no systematic study of Mongol dress has been written, this is the first such study that brings together analysis of the decorative motifs, weave structures, and tailoring of excavated costumes and textiles, alongside pictorial representations and contemporary textual descriptions. To understand the genesis and development of the Mongol courtly vestimentary system, which evolved in such a short period of time, antecedents from the Steppe, Central Asia, China, and the Islamic world are considered. Concordances and discrepancies among this evidence allow for hypotheses about what the Mongol court actually wore, how it wished to be portrayed, and how others saw it. These hypotheses reveal much about the aspirations of the Mongol empire on one hand, and the anxieties they elicited, on the other.