This chapter discusses the influence of Roman historians on the development of early modern political theory. It will explore how and why readings of the Roman historians, in whose works few explicit treatments of the nature and forms of government are to be found, nevertheless contributed largely to the articulation and development of political theory as a discourse. More specifically, the chapter will address the ways in which the interpretation of Roman historiography by the political theorists of early modern Europe contributed to the formation of modern political thought. Thus, the paper will look at the reception of Livy, Sallust, and Tacitus in the thought of Machiavelli, Hobbes, and Montesquieu. Political theory is constituted by three basic elements or forms of inquiry. The first deals with the inquiry into the best forms or types of governments (or constitutions, as in Plato and Aristotle). The second talks about the analysis of political power and of its sources, origins, and foundations (and, consequently, of the state and its legitimacy, and its justification in terms of political obligation). And the third delves into the nature and character of “politics,” or of the “political.”