This chapter looks at postcolonial and decolonial approaches to studying world politics, arguing that these are multi-layered and diverse. These do not constitute a single ‘theory’ of the international but rather a set of orientations think about it. The chapter starts by separating a number of different elements involved in theorizing the world, and how postcolonial and decolonial approaches look at them. These include questions of epistemology, ontology, and norms or ethics. It then examines the historical context in which postcolonial and decolonial approaches arose, showing that there was a dynamic relationship between political struggles for decolonization and the development of different intellectual arguments. It considers where postcolonial and decolonial approaches have emerged and where they depart from each other in terms of analysis and focus. Having traced these traditions through the twentieth century, the chapter describes the key concepts used in postcolonial and decolonial thought across different disciplines, before looking at their impact on the field of international relations (IR). The chapter also explores the similarities and differences between different approaches and other theories in the field of IR. Finally, it contemplates the on-going popularity of postcolonial and decolonial approaches in the present day.