This chapter examines the core assumptions of poststructuralism, one of the international relations (IR) perspectives furthest away from the realist and liberal mainstream. It explores whether language matters for international relations, whether all states have the same identity, and whether the state is the most important actor in world politics today. The chapter also considers poststructuralist views about the social world, state sovereignty, and identity and foreign policy. Finally, it discusses poststructuralism as a political philosophy. Two case studies follow. The first one looking at discourses, images, and the victory of the Taliban regime. The second case studies examines Covid-19, state sovereignty, and vaccines.