These organizations are not officially a part of the European Union. In some cases the member states of the EU also have membership in these organizations. In other cases the EU works with these organizations.
The European Liberal Democratic and Reform Party
The European Federation of Green Parties
North American Treaty Organization
European Bank for Reconstruction and Development
European Court of Human Rights
Organization for Economic Cooperation and Development
Organization for Security and Cooperation in Europe
The European Community Studies Association - United States
University Association for Contemporary European Studies (United Kingdom)