Climate Assemblies are capturing the imagination of people interested in how citizens can participate in decision-making to address the climate and ecological crisis. Traditional institutions are struggling to cope with the challenges of a climate-changed world. Climate Assemblies are new civic institutions that include a cross-section of the public in deliberation to influence environmental policy, governance, public discourse and collective action. With the rapid spread of this approach to public engagement, practice has developed well in advance of research. This book addresses that gap by analysing the internal and external dimensions of climate assemblies and how they interact. It brings together 25 authors to offer novel perspectives, critical insights and practical reflections based on original research about paradigmatic cases at local, national, transnational and global levels. The book investigates the state of the field, reflects on the hope and hype about this growing phenomenon, and proposes ways to improve climate assemblies so that they can make a difference in a climate-changed world.