This chapter explores the views of prominent Western thinkers between the sixteenth and eighteenth centuries who addressed the relationship between political thought and the historiography of international law. The chapter’s early modern chronological scope puts into sharp relief the precursors and originalities of the so-called nineteenth-century turn in international law’s historiography. A survey of consequential understandings of the link between international legal historiography and political thought finds that early modern thinkers systematically connected politics and international law by examining their shared epistemological, ontological and genealogical foundations, drawing interweaving lines of reasoning on how these fields are understood, and how they arise and evolve. Thus the arc of texts from Francisco de Vitoria to Jean Barbeyrac that specifically focus on this topic suggests that considerable sophistication existed before the nineteenth-century master narrative of international law’s historiography, and has been partly lost.