This study examines the formal and ideological origins of the earliest Renaissance cast portrait medals, created by the artist Pisanello (Antonio di Puccio, c. 1394-1455). It focuses on three courts and objects produced at each that are central to understanding the emergent sculptural form. Chapters are devoted to the Constantine and Heraclius medallions created for the Valois prince Jean, Duc de Berry (r. 1360-1416); Pisanello’s first medal, dedicated to the Byzantine Emperor John VIII Palaeologus, produced c. 1438 at the Este court in Ferrara; and the series of four medals that Pisanello produced for Ludovico Gonzaga of Mantua (r. 1444-1478). Frequently marginalized in art-historical analyses, studies of the earliest cast medals traditionally approach the objects individually, celebrating their form and iconography as manifesting humanist interest in the individual and the revival of ancient modes of personal commemoration. Through references to the wider historical context and the contemporary visual culture of the courts, this analysis demonstrates that the origins of the new sculptural form lay in synthesizing a series of visual models previously overlooked. These included a class of Byzantine sacred objects, enkolpia, identifiable with successful military endeavors in the East; prophetic literature; French chivalric romances; and genealogical imagery. An equally important contribution of this analysis resides in demonstrating that, from its inception, the cast portrait medal was aligned with one of the most pressing political and religious concerns of the period, the protection of Eastern Christendom from Ottoman incursion. The small, portable, and reproducible objects studied responded to the shared religious and political aspirations of their French and Italian court patrons, each of whom was, to a greater or lesser extent, identified with the call for crusade. Each patron utilized the emergent form of the medal to promote his personal or dynastic rule, employing a form identified with a distinguished tradition of Christian military triumph, traced to ancient Rome, but including as well Byzantine imperial and French royal models. The combination was especially appealing to Pisanello’s signorial patrons, professional military leaders eager to legitimize their authority. This study redefines understanding of the form and hence the political and religious function of the objects considered and offers a model for expanded analysis of Pisanello’s wider medallic oeuvre. It also demonstrates that the ideological origins of Pisanello’s medals and their antecedents resided in the same concerns that motivated production of monumental works of art commissioned by the same patrons, including altarpieces, frescoes, and architecture, thereby situating analysis of the earliest medals centrally within the study of visual culture in the early modern courts.