Co-operation between governments on the basis of maintaining state sovereignty. This is in contrast to supra-national integration, where governmental functions and powers (competences) are shifted from the national to the superior EU level.
The pre-Lisbon EU had a 'pillar' structure. It was supra-national in the first pillar, where EU law has primacy over national law in any case of conflict. It was more intergovernmental in the second pillar of Foreign and Security Policy and the third pillar of Justice and Home Affairs.
The Lisbon Treaty removed the intergovernmental pillars and established the European Union with one legal personality and a uniform constitutional structure that would be capable of covering all area of public policy either actually or potentially.
Intergovernmental theories of European integration regard the relations between governments at the supra-national as well as the international level as the most important reason for EU integration.