The anticolonial writer and psychiatrist Frantz Fanon became famous in the 1960s for his radical criticism of colonial racism and its influence on colonised peoples. His descriptions of how colonialism destroys people not only physically but also mentally and emotionally continue to inspire many political movements and theoretical concepts to this day. His work highlights the enduring nature of colonial relations, and the different ways in which (in)security and its protection can be perceived differently depending on the viewer’s position in society. However, Fanon’s name also remains inextricably linked with his most controversial and uncompromising stance: his commitment to the right of colonised peoples to threaten the security of others by the use of violence in their struggle for liberation. As a recent heir of Fanon’s work, post/decolonial research challenges critical security research in the modern context; this entry uses post/decolonial research to point to multiple ways in which both theoretical fields have enriched the articulating and practicing of (in)security.