This dissertation makes two contributions to the scholarship on Italian Renaissance political thought and the reform of the Roman Catholic Church, generally, and the thought of Girolamo Savonarola and Niccolo Machiavelli, specifically. First, I argue political theorists have unjustly ignored Savonarola's political thought. Savonarola's works merit consideration because he offers a novel justification of republican government in the context of a broader attempt to advocate theological-political reform in Florence. He departs from Aquinas and the Scholastic tradition in which he was trained by offering a more positive view of republican institutions, arguing that the primary function of temporal government is to make its citizens better Christians, and advocating tyrannicide should it be needed to maintain a harmonious republic. He also differs from later Protestant Reformation movements, neither seeking to restructure Church leadership nor contesting Church doctrines in the way that Luther challenges the papacy and sacraments. Although scholars of political theory do make note of Machiavelli's reflections on Savonarola's attempts at political reform in the Prince and Discourses, none provide any in-depth reflection on the similarities and differences between their writings. The dissertation's second contribution is an attempt to fill this gap in the scholarship by considering how Machiavelli's assessment of the theological-political situation in Florence may have been influenced by Savonarola's mixture of success and failure. While Savonarola explicitly denounces the value of "earthly wisdom" such as Livy's histories, offering up theology and prophecy as the only reliable sources of political knowledge, Machiavelli argues that the only suitable foundation for political action is the so-called earthly wisdom that Savonarola condemns. Taking history and personal experience as his guide, Machiavelli recommends political reforms that are similar in some ways to Savonarola's understanding that wicked clergy are to blame for the corruption and that harsh punishment is necessary for maintaining order. However, Machiavelli dismisses the Friar's assumption that a city premised on Christian values can produce earthly concord and political strength, instead rejecting core Christian teachings such as forgiveness, which he believes to be detrimental to political liberty and the cultivation of an armed citizenry.