The European Union (EU) – and its legal order – occupies a unique position in international law. In this context, the ‘autonomy of EU law’, since its judge-made creation in the 1960s, continues to fascinate international and EU law scholars alike – despite or perhaps even because of its notorious elusiveness and ‘shapeshifting’ character. The conceptual claim to the autonomy of EU law has been not only instrumental to the development of the EU as a ‘new legal order’ but also – from an EU law perspective – continues to guide the grand design of interactions between EU law and international law. The workshop, taking an inside and outside perspective, offers a fresh academic appraisal of the multiple dimensions of the relations between the two intersecting legal orders, with the (claimed) ‘autonomy of EU law’ being at the core of – and under pressure in – these dynamic interactions.