This Handbook examines the regulatory, social, financial, and technological issues pertaining to energy communities in smart cities. Evidencing the emergence of new imperatives at the intersection of sustainability, resilience, innovation, and legal issues, energy communities embody the thrust of the user-centred digital transformation our societies are subjected to today. By bridging the energy communities debate with smart cities research, this Handbook positions itself at the heart of the conversation on energy sustainability, climate action, and “just transition”. Drawing on contributions from across the globe, this book offers both a birds-eye and a detailed inter- and multidisciplinary insight into the emergence of energy communities and their evolution in the smart city context. Technological and regulatory aspects of this transition are explored from a variety of conceptual and empirical perspectives. Case studies evidencing developments in the Global South and the Global North embellish the conversation. Questions of climate change, energy efficiency, renewable energy sources, emissions’ reduction, and corresponding policy frameworks are discussed. Dedicated to all those interested in climate action, energy transition, sustainable development, and smart cities, this Handbook will be of interest to policymakers, lawyers, energy and urban experts, researchers, and students.