This chapter discusses the concept and discipline of international relations, and some of their key encounters and tensions with Marxist scholarship. As a relatively new and policy-driven discipline, emerging with racial and imperial objectives in early twentieth century Western Europe and later in the US, International Relations (IR) presented several challenges for Marxists. These challenges were increased by the fact that Marx and Engels did not have an explicit theory of the international, nor of the state. Moreover, the early Marxists developed theories of imperialism based on national and territorial concepts of the state, which became difficult to disentangle so as to produce historically and theoretically new approaches to the origins and development of capitalism. However, since the 1970s and 1980s, the influence of a post-Soviet Marxist academic impetus and of other critical approaches has produced a plethora of Marxist authors and research areas, reflecting the wide variety of Marxist theories and cross-disciplinary concepts such as hegemony, transnational class, dependency, world-systems theory, and more recently, debates in historical sociology on race, gender, class, in addition to the state and states system. As is the focus of this chapter, Marxist international relations have been dominantly Anglo- and Western-centric, in spite of efforts to develop analyses of Third World political economy, postcolonial struggle, decolonisation, and Southern epistemologies. Although international relations are a rich and influential area of Marxist thought, the chapter argues that Marxist international theory would benefit greatly from better integrating scholarship from the Global South, as well as problems of legal borders, property and methodology.