This chapter looks at the France, Germany, and the United Kingdom (E3) as an important foreign policy resource. It outlines the different elements of the European Union's (EU) foreign policy apparatus: the high representative; the European External Action Service (EEAS); the European Commission; and the European Parliament. European engagement on the Iran nuclear file harks back to the E3 initiative of 2003, which led to the Tehran declaration of October that year. As it happens, 2003 would become a watershed year not only for EU-Iran relations but also for the EU in general. In the case of Iran, the EU's own interests converged with an international opportunity to get engaged and to seek a negotiated outcome to the nuclear standoff. Three main European interests stand out: to avert another war in the Middle East; to avoid another intra-EU and transatlantic split over world affairs; and to defend the international nonproliferation regime.