Both a theory of integration and a method of decision‐making in international organizations, that allows states to cooperate in specific fields while retaining their sovereignty. In contrast to supranational bodies in which authority is formally delegated, in intergovernmental organizations states do not share the power with other actors and take decisions by unanimity. In the European Union, the Council of Ministers is an example of a purely intergovernmental body while the Commission, the European Parliament, and the European Court of Justice, represent the supranational mode of decision‐making. Virtually all other integration initiatives, including those among developing countries, are almost fully intergovernmental.

In Political Science, intergovernmentalism treats states, and national governments in particular, as the primary actors in the integration process. Intergovernmentalist approaches claim to be able to explain both periods of radical change in the EU  because of converging governmental preferences and periods of inertia because of diverging national interests. Intergovernmentalism is distinguishable from realism  and neorealism because of its recognition of the significance of institutionalism  in international politics and the impact of domestic politics upon governmental preferences.

As a theoretical approach to the study of European integration, intergovernmentalism was developed in the mid‐1960s. Building on realist premises, writers such as Stanley Hoffmann highlighted the convergence of national interests and the will of states to cooperate as central to the analysis of regional integration. More recently Andrew Moravcsik’s ‘liberal intergovernmentalism’ incorporates the role of domestic interests in helping define national state preferences, while still arguing that states have the ultimate control over the process and direction of integration. In studying European integration, both the realist and the more liberal variants of intergovernmentalism have focused on major sets of inter‐state bargains (especially intergovernmental conferences) and on the decision‐making of the Council of Ministers, rather than on the role of the Commission, European Parliament, or societal actors.