This thesis examines how the ministers and officials of Charles V sought to cultivate a specific state identity that defined Spain and its people against non-Christian ‘Others’—namely the Jews, conversos, and Moriscos of Iberia, as well as the Lutheran heretics of Europe. These officials utilised various narratives and policies that emphasised the ideas of Christian purity and crusade, thus building off of the work done by the Catholic Monarchs. Charles V and his ambassadors expressed these narratives on the stage of European diplomacy and projected Spain’s state identity abroad. More importantly, this thesis explores how these ambassadors were often challenged in their attempts to define Spain on the world stage, as the foreigners they encountered presented them with counter-narratives that destabilised their image. Such counter-narratives often played upon the contradictions and complexities that were inherent in Spanish society regarding its constructions of religious and ‘racial’ barriers. The clashes between the Spaniards who sought to defend Spain and its reputation and those who disparaged it demonstrate the weakness of Spanish state-identity during the reign of Charles, as well as the anxieties that Spain’s ambassadors often felt when projecting Spain’s image abroad.