This book provides a synthesis of scientific knowledge on megacity urbanization on the coast, environmental impacts, risks and management choices, including a focus on adaptation, mitigation and disaster risk management. It is the primary output of a major international scientific project sponsored by the International Geosphere Biosphere Programme, the Land-Ocean Interactions at the Coastal Zone programme of IHDP/IGBP, and others. It brings together the work of over 60 contributing authors and an international review board. It presents the international policy and academic community with an unbiased and high quality assessment of the state-of-the art in areas of social-ecological systems interaction. One of its main messages is that while we know a great deal about megacities of more than 10 million people and about urban processes, and about coasts and their physical and ecological processes (aquatic, physical and atmospheric), there is relatively little work that focusses primarily at points of intersection between large-scale urbanization and the coast. The book responds to this gap by providing the first global synthesis of megacity and large urban region urbanization on the coast. Its focus is on environmental and development challenges, climate change and disaster. It is interdisciplinary and brings together world recognised scientists (including many IPCC lead authors) on urban climate and atmosphere, disaster risk management, demography and coastal environments.