The European Union (EU) is a regional cooperation regime with a specific and still fluid governance structure. It constitutes the world’s largest and institutionally most deeply integrated system of international relations with supranational features. As a consequence, the literature on the EU often emphasizes informality, multilevel aspects, and its “network governance” character. Network analysis is therefore a promising perspective for the systematic investigation of complex networks of formalized actor relations as well as of informal and implicit political structures and processes in the EU. Applied network analysis is meanwhile used for the investigation of multi-level policy preparation, of collective decision-making in the political system in the EU, and of the implementation process of EU policies in the Member States.