This chapter traces the changing role played by the concept of ‘hegemony’ in international legal thought. It begins by establishing the original meaning of the term in Ancient Greece and follows its deployment in the Russian Revolution. It argues that by the end of the Second World War, ‘hegemony’ had come be understood in two broad registers: as a ‘universalist’ strategy of class domination and as a vision of international relations in which a ‘predominant’ state shapes the global order. The chapter shows how, in the twentieth century, these two understandings became closely associated with the discipline of international relations on the one hand, and poststructuralism on the other. It then shows how these two understandings have animated international legal thought. The international relations vision was used by a series of scholars to understand the ‘unilateral’ moment of US domination – particularly as reflected in the ‘War on Terror’. The universalist vision was a more ‘internal’ vision, which examined how international institutions make claims to neutral universality when putting forward partial or particular legal interpretations. The chapter contests both of these visions, showing – through a brief history of international financial institutions – that both are fundamentally idealist. The chapter suggests that returning to Marxist conceptions of hegemony and imperialism might help us make better sense of international law.