AbstractThe European Union's (EU) claims to be a leader in international climate policy are well known. Since the early 1990s, a rich and vibrant academic literature has analyzed the internal sources and international consequences of its leadership aspirations, especially in relation to the challenges of mitigation. More recently, attention has turned to adaptation policy. The literature highlights how policy actors have successfully exploited many of the opportunities afforded by the EU's ‘polycentric’ form, while minimizing its downsides, but that acute challenges lie ahead, particularly if a strong global‐level framework remains elusive. It has continually underlined the fact that the EU's climate policy activities have enormous relevance well beyond European borders. Both in terms of its role as a driver of international policy and a source of transferable policy lessons on how to govern in ‘polycentric’ settings, appreciating the EU's experience is vital for those seeking to understand the governance of climate change, both within and between states. WIREs Clim Change 2013, 4:75–90. doi: 10.1002/wcc.205This article is categorized under: Policy and Governance > Multilevel and Transnational Climate Change Governance