In the second half of the fifteenth century, the Aragonese kingdom of Naples dominated the intellectual and political milieu of the Renaissance, especially in Italy. As the Trastámaran monarchs of the Neapolitan Regno set out to create an empire that spanned the Mediterranean, the humanists in and around Naples considered questions of good governance and how to integrate virtue into politics in this Iberian kingdom. This dissertation argues for three distinct but interconnected phases of Quattrocento humanist virtue political thought surrounding Naples, which map roughly onto the three generations of Trastámaran rule. Over the course of the rise and fall of the Aragonese empire, humanist conceptions of virtue’s role in politics shifted the responsibility for the preservation of the state and the maintenance of the bonum commune from the monarchs to the populace. Humanists in the first generation emphasized the virtue of Naples’s king as the primary means to order Christendom and the Italian peninsula. This set the stage for more robust articulations of mimetic virtue acquisition in the second generation, as humanists in this later period explored the mechanisms by which a populace observes and imitates its ruler’s virtuousness or viciousness. These ideas made a prince accountable to project through his deeds an unbroken exemplary image of virtue in order to morally form his citizenry. By the collapse of the Trastámaran monarchy in the third generation, Naples’s leading humanist charged all prudent persons – regardless of age, sex, social standing, or education – with the previously princely duty to project an image of virtuous character in their comportment, even if this required deception, so as to inspire all citizens to virtue.