This chapter provides an overview of intergovernmentalist integration theory, focusing particularly on the classical, liberal, and ‘new’ variants of intergovernmentalism. It first introduces the basic premises and assumptions of intergovernmentalism, identifying its realist underpinnings and the state-centrism that provides the core of the approach, before examining in more detail the specific characteristics of the classical approach associated with the work of Stanley Hoffmann. The subsequent section also examines some of the ways in which intergovernmentalist thinking has contributed to different conceptualizations of European integration. The topics covered in this section are: confederalism; the domestic politics approach; and institutional analyses that emphasize the ‘locked-in’ nature of nation states within the integration process. Next, the chapter provides an introduction to liberal intergovernmentalism, as developed by Andrew Moravcsik, which, since the mid-1990s, has become a focal point for intergovernmentalist research and addresses some of the criticisms of the liberal intergovernmentalist approach. The chapter ends by focusing on new intergovernmentalism, the most recent version of the intergovernmentalist approach.