Republicanism has been on scholars’ research agenda since the 1970s, and several studies on eighteenth-century French republicanism have linked it to the Atlantic republican tradition. A central question that has puzzled intellectual historians studying republicanism is how this concept considered as antiquated or only adapted to small city-states became the concept of choice for a large modern nation such as France. The works of Pocock, Skinner, and Pettit launched a vast a research programme on Atlantic republicanism as a theory of liberty understood as ‘non-domination’. Focusing on eighteenth-century France and the French revolution, historians such as Baker, Hammersley, Monnier, Spitz, Whatmore, and Wright have argued against Furet, Ozouf, Maintenant, Nicolet, and Vovelle that this republicanism existed before and during the revolution as a language of opposition based on classical Greek and Roman authors. In particular, Edelstein has shown how the two languages of republicanism and nature collided to form a ‘natural republicanism’ that pervaded during the revolution and intellectually explains the Terror. Hammersley, on the other hand, has shown how English republican texts provided answers to the fundamental question for early modern republicans: how republican institutions and practices (securing liberty) could be made workable in the context of a large nation-state? However, these studies on classical republicanism and natural republicanism have overlooked or insufficiently explained the universalist side of the language of republicanism in the French revolution: how could republicanism be made workable for the world, and how could it be argued that humankind formed a nation? This thesis provides an answer to how a ‘universal republic’ could be theorised in the French revolution by examining the writings of Anacharsis Cloots (1755–1794). It argues that Cloots was one of the leading proponents of ‘cosmopolitan republicanism’. The thesis uses Cloots’s entire corpus of works, which have been published in a three volume collection entitled OEuvres, as well as a collection of all his revolutionary writings in 'Ecrits révolutionaires'. This thesis uses Skinner’s contextualist method to present an interpretation of Cloots’s writings by setting them in their political, social, and intellectual contexts. The introduction presents a critical review of studies on Cloots from the nineteenth century to the present. Vilified or lauded, Cloots was considered a founding figure of cosmopolitanism by nineteenth-century authors, a fame that faded in the twentieth century.