Recently, international hierarchy has taken center stage in international relations (IR) theory. Hierarchy is typically understood as a feature of domestic institutional stratification; it defines a set of social arrangements that reflects relations of authority. Where anarchy had once dominated IR theory, there are now substantial debates about how to account for hierarchical international relations between nominally sovereign states, as well as a prevalent conflation between hierarchy and hegemony to discuss unequal material and social arrangements. Yet the focus on hierarchy is nothing new. Theories such as Power Transition Theory and Hegemonic Stability Theory had attempted to understand the international system as a consequence of significant material imbalances of power. Moreover, critical theoretical approaches relying on Marxian analysis tended to emphasize the diverse hierarchical forms of international relations in the political-economic realm. More recent literature on international hierarchy is derived from a rationalist ontology, which explains why it would be a legitimate policy choice for states to enter into asymmetric relations. This literature understands hierarchy in its formal-juridical dimensions. In addition, discussions of international hierarchy by critical and postcolonial theorists take different ontological and epistemological starting points, as hierarchy can be understood in broader terms as a way of constituting and demarcating identities, for example. In other words, hierarchy is as much a social concept as a juridical one. However, this raises crucial theoretical questions concerning the differences between hegemony and hierarchy.