East Asia is becoming an increasingly coherent regional entity in political economic terms, and remains a region of enormous geo-strategic significance for the European Union. Europe's links with China and Japan are especially important, and moreover these two countries are looking in various ways to exercise various forms of regional leadership in East Asia. This has critical implications for the EU's relations with the East Asia region generally, and also for the wider international system. Similar and related impacts maybe construed from deepening East Asian regionalism, involving processes where both Japan and China play vitally important roles. The analysis presented here examines the both micro and macro level developments in East Asian regionalism, and issues relating to Japan, China and regional leadership. It concludes by discusses the implications of these matters for the European Union, and recommends that the EU should pay particularly close attention to emergent exercises of regional leadership in East Asia, most likely to be performed by Japan and/or China.