This book examines cooperation between the US and the EU on financial regulatory reform, notably at the outset and the first three years of the global financial crisis. It discusses the development of US—EU cooperation on financial regulation over the last few decades at several levels, including at heads of state level, markets regulator level and at international level, and progresses with a detailed examination of cooperation at the outset of the financial crisis. It looks at the nature of and motivation for intense US—EU cooperation on coordinating a response to the crisis and presents a compelling argument that a defacto alliance was formed, which served to benefit respective US and EU interests domestically and in the international financial system. Providing a new perspective on financial regulatory reform after the last financial crisis and the relationship of regulatory outcomes to international financial governance, this volume will be of use to researchers interested in transatlantic relations, financial regulation, international relations, global governance, and the European Union, as well as professionals and policymakers working in foreign relations, financial markets, or banking policy.