Nuclear weapons remain the unquestioned core of the defense postures of both France and the United Kingdom. At the same time, the European Union is progressively enhancing its Common Foreign and Security Policy (CFSP), notably through the establishment of a European Security and Defence Policy (ESDP). Yet, despite evident progress in the CFSP, whose ultimate purpose is to lead to a common defense policy, EU member-states still deal with nuclear issues on a predominantly national basis. What is the alleged purpose of European nuclear forces? How is the raison d'être of the French and British nuclear deterrents conceptualized against the background of progressing European (defense) integration? This article examines the construction of the rationale of the French and British nuclear forces and their compatibility with the emerging European defense policy, particularly with regard to a hypothetical integration of both arsenals into a common deterrent. Could and should a European nuclear deterrent be envisaged as the final stage in the framing of a European defense?