In this chapter, students will learn about postcolonialism as an increasingly prominent theoretical approach to security in International Relations (IR). Focusing on the lasting legacy of empire and the perpetuation of hierarchies between the Global North and South, postcolonialism is best understood as an approach or orientation rather than one coherent theory, or even school of thought. Postcolonial thought is inherently interdisciplinary and, while there is no postcolonial school of security studies, nonetheless it provides important insights for students of security. This chapter engages postcolonial thought in the field of security by focusing on key moments in the development of postcolonial thought and the work of postcolonial thinkers. It highlights both shared assumptions and important differences between proponents while stressing the myriad ways in which postcolonialism can enrich our understanding of security through its sensitivity to questions of colonial legacies, racism and inequality.