This textbook answers important questions about the ecological structure, functions and socio-ecological development of cities worldwide. It explains ecological challenges for cities of the 21st century such as resource efficiency, climate change, moderation of quality of life and resilience. The book combines theories of urban development and ecology with practical applications and case studiest worldwide. It shows that cities are by far not only problem areas but also offer great potential for a good life and that the various urban ecosystems can make a considerable contribution to this. The "eco-city" is a real goal that can be pursued step by step in a targeted manner, taking into account the local and regional context. This book is a translation of the original German 1st edition, Stadtökosysteme by Jürgen Breuste published by Springer Fachmedien Wiesbaden GmbH, part of Springer Nature in 2016. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation. Springer Nature works continuously to further the development of tools for the production of books and on the related technologies to support the authors. Four renowned urban ecologists have contributed their specific experience. Jürgen Breuste is an urban ecologist in several universities as president of the Society for Urban Ecology (SURE) on the topics of sustainable urban development, urban biodiversity, ecosystem services and eco-cities. Dagmar Haase is a landscape ecologist and works at the Humboldt University of Berlin on urban ecosystem services and land use modeling. Stephan Pauleit is a landscape planner and works at the Technical University of Munich on strategies for the sustainable development of urban landscapes. Martin Sauerwein is a geographer and works at the University of Hildesheim, Germany, on geo-ecology in cultural landscapes, geo-archaeology and soil protection. The textbook addresses a broad audience of students, teachers and also offers its services to practitioners in the fields of ecology, urban ecology, urban development, sustainability, urban geography, nature and landscape conservation, spatial planning, landscape ecology, and urban studies. Case studies, examples and explanations allow a deeper insight. Questions at the end of each chapter help to check the progress of knowledge, and a comprehensive bibliography are helpful for further studies.