This chapter introduces Rival Legalities: Practices of International Law in the Cold War, exploring international law’s practices during the Cold War. The authors aim to redescribe Cold War international law, revealing a rich plurality of legal forms and practices. Contrary to the narrative of the Cold War as an interruption in international law’s development, the authors propose viewing it as a period of rivalrous yet mutually constitutive accounts of the ‘international’. This perspective highlights diverse world-making projects beyond the East-West dichotomy, including anti-colonial and anti-anti-colonial efforts. Recognising the plurality of rival world-making projects demands a different conceptual frame than one focused solely on American-Soviet rivalry. The authors argue that international law during the Cold War was not a settled body of norms but a set of practices emerging from the period’s unique conditions. By examining these practices, the book offers a new lens on the Cold War’s impact on international law, highlighting the creative and strategic uses of law by various actors, particularly from the Global South, in their struggles for decolonisation and new international legal orders.