Cities are home to the majority of the world’s population, drivers of both national and global economic activity, hubs of culture and innovation, and are the locations in which many of society’s greatest challenges, from climate change to social unrest, play out. Given this, it is not surprising that, in recent years, cities have captured the global imagination. A focus on cities and urban issues is now a common feature across business, pol-itics and culture. As cities have become more visible, so too has the role of city leadership, from calls for mayors to ‘rule the world’, to sizeable philanthropic investments directly into supporting cities to improve their leadership capacity. Meanwhile, cities are no longer focusing only on activities within their own boundaries, but are seeking a greater voice and influence in tackling national and international challenges. May-ors are making strong statements and taking action on issues normally beyond their remits, such as natural disasters, immigration and climate change, often standing up against regional and national political leaders in the process. Despite this, we have relatively little data to underpin our understanding of city leadership and, in particular, to make meaningful comparisons between cities. Who leads cities and what political struc-tures underpin this leadership? If we live in the age of the city, knowledge about who leads them, how they are governed and how they set strategic priorities is essential. This book is a first attempt to fill this gap.