The European Union Institute for Security Studies (EUISS) is a Paris-based agency of the European Union. The EUISS evolved from Western European Union Institute for Security Studies following a gradual transfer of powers from the Western European Union (WEU) to the EU. It now operates under the Union's Common Foreign and Security Policy (CFSP).
The EUISS is an autonomous agency with full intellectual freedom. As a think tank it researches security issues of relevance for the EU and provides a forum for debate. In its capacity as an EU agency, it also offers analyses and forecasting to the High Representative for Foreign Affairs and Security Policy, Catherine Ashton.