This chapter examines the theory and practice of state derecognition in world politics. It offers a comprehensive assessment of legal, normative and political theories, and surveys practices of state derecognition. It first examines how the possibility of reversing the recognition of states is discussed in a wide range of disciplines, including international law, political theory and international relations. The chapter then looks at the process and micro-politics of derecognition, focusing on the actors, narratives and diplomatic tools used in reversing state recognition. To give an insight into the derecognition of states in practice, the key cases of Taiwan, Western Sahara, Abkhazia and South Ossetia, and Kosovo are studied. The chapter concludes with a critical discussion of the effects of derecognition and the need to develop new perspectives on statehood and state recognition.