Cities are playing an ever more important role in the mitigation and adaption to climate change. This book examines the politics shaping whether, how and to what extent cities engage in global climate governance. By studying the C40 Cities Climate Leadership Group, and drawing on scholarship from international relations, social movements, global governance and field theory, the book introduces a theory of global urban governance fields. This theory links observed increases in city engagement and coordination to the convergence of C40 cities around particular ways of understanding and enforcing climate governance. The collective capacity of cities to produce effective and socially equitable global climate governance is also analysed. Highlighting the constraints facing city networks and the potential pitfalls associated with a city-driven global response, this assessment of the transformative potential of cities will be of great interest to researchers, graduate students and policymakers in global environmental politics and policy.