This book presents the proceedings of the 12th International Conference on Energy Engineering and Environmental Engineering (ICEEEE 2025), held from October 18 to 20, 2025, in Chongqing, China. Jointly organized by Beijing Jiaotong University and the University of Edinburgh, ICEEEE 2025 established itself as a authoritative platform for the exchange of cutting-edge research and innovative solutions in energy and environmental engineering. The conference brought together leading experts, researchers, and practitioners from around the globe to address the most pressing challenges and emerging trends in the field. This book encapsulates a wealth of state-of-the-art research, practical insights, and forward-thinking discussions, offering a comprehensive overview of the latest advancements in renewable energy technologies, energy efficiency, environmental sustainability, and green urban development. Designed for a diverse audience, including academics, industry professionals, and policymakers, this book serves as an invaluable resource for those committed to shaping a sustainable future. It not only provides a snapshot of current achievements but also inspires further innovation and collaboration in the pursuit of global energy and environmental sustainability As the world transitions toward a net-zero future, the insights and solutions presented in this volume underscore the critical role of interdisciplinary research and international cooperation in addressing the dual challenges of energy security and environmental preservation.