This dissertation examines state formation in sixteenth-century Modena, Italy during a critical yet under-examined period in the city's political history. Based on chronicles, letters, legal sources, family archives, and conventual sources, this case study analyses a decades-long vendetta between the politically prominent Bellencini and Fontana clans. Focusing on the collision between a strong nobility and state centralization during the sixteenth century, this study examines the practice of vendetta among the governing elites. In particular, these violent practices expose the competing discourses of localized and state authority at a moment when the Dukes of Ferrara, Modena, and Reggio sought to enforce standardization in their politically fragmented territories. While Modenese defiance of unilateral d'Este reform did not function as the primary impulse for factional violence, Modenese discontent with the ways in which the Este effected reform provide an explanation for why vendettas remained difficult to bring under control. In order to curb vendetta, the dukes needed to account for the strength of regional interests. An examination of vendettas among Modena's governing elite and the Este dukes' inability to pacify them without the cooperation of the local nobility illuminates this negotiation with the state for power. The contradictions inherent in the simultaneity of vendetta practices and Modenese state-building allows for a broader picture of how state formation came about. As this study shows, it was a process of reform and resistance, coercion and cooperation.