This dissertation investigates Niccolò Machiavelli's account of civil conflict across his corpus to develop a theory of conflictual republicanism. I argue that his theory offers a uniquely valuable set of tools for thinking about conflict in democratic political life. Specifically, his distinction between productive public conflicts and destructive private partisan conflicts alongside his account of the causes and consequences of both can help us think through our own preoccupations with questions of difference, disagreement, and partisanship in democratic political life. Each of the dissertation's five substantive chapters investigates a different aspect of this theory of conflictual politics and considers them in the context of contemporary debates in political theory and American politics. Respectively, the chapters cover his theory of class politics, religion, equality, imperialism, and political parties. The dissertation then concludes with an examination of the critical leverage Machiavelli's treatment of these themes provides for contemporary democratic projects.