Natural hydrogen (H 2 ) holds significant promise as a clean and renewable energy source that helps achieve a net-zero carbon future. However, the study of natural hydrogen reservoirs (NHRs) remains in its early stages, limiting their exploration and development. This book provides a comprehensive review of NHRs, including their geological occurrence environments, formation mechanisms, enrichment processes, advanced exploration and production technologies, and influencing factors. Although high concentrations of natural hydrogen have been identified globally, only the Bourakebougou hydrogen field in Mali has reached commercial production. This book outlines the current understanding of natural hydrogen systems, highlighting recent advancements, key challenges, and prospects for future energy supply. It provides a systematic examination of geological origin, accumulation, and preservation conditions of natural hydrogen, along with reservoir-forming processes, global distribution patterns, detection technologies, and future outlook. To unlock the full potential of NHRs, continued progress in geological exploration, detection, and extraction technologies is essential, along with a deeper understanding of hydrogen genesis and trapping mechanisms. Future research should focus on improving the efficiency and cost-effectiveness of hydrogen recovery, enhancing storage and transport solutions, and ensuring environmental and operational safety. Achieving a sustainable, hydrogen-powered future requires an interdisciplinary approach, integrating insights from geology, geoscience, engineering, and policy. This book aims to serve as a valuable reference for researchers, industry professionals, and decision-makers committed to advancing this emerging field of clean energy. Natural hydrogen (H2) holds significant promise as a clean and renewable energy source that helps achieve a net-zero carbon future. However, the study of natural hydrogen reservoirs (NHRs) remains in its early stages, limiting their exploration and development. This book provides a comprehensive review of NHRs, including their geological occurrence environments, formation mechanisms, enrichment processes, advanced exploration and production technologies, and influencing factors. Although high concentrations of natural hydrogen have been identified globally, only the Bourakebougou hydrogen field in Mali has reached commercial production. This book outlines the current understanding of natural hydrogen systems, highlighting recent advancements, key challenges, and prospects for future energy supply. It provides a systematic examination of geological origin, accumulation, and preservation conditions of natural hydrogen, along with reservoir-forming processes, global distribution patterns, detection technologies, and future outlook. To unlock the full potential of NHRs, continued progress in geological exploration, detection, and extraction technologies is essential, along with a deeper understanding of hydrogen genesis and trapping mechanisms. Future research should focus on improving the efficiency and cost-effectiveness of hydrogen recovery, enhancing storage and transport solutions, and ensuring environmental and operational safety. Achieving a sustainable, hydrogen-powered future requires an interdisciplinary approach, integrating insights from geology, geoscience, engineering, and policy. This book aims to serve as a valuable reference for researchers, industry professionals, and decision-makers committed to advancing this emerging field of clean energy. In addition, this book: Examines the viability of natural hydrogen deposits as a substitute for conventional hydrogen techniques - Evaluates drilling, extraction, storage, and transportation barriers to harnessing hydrogen from subsurface reservoirs - Advances knowledge on natural hydrogen systems and their impact on the adoption of decarbonized energy systems Yujie YUAN is a Lecturer and the Discipline Coordinator of the Chemical, Energy, and Resources Discipline in the School of Engineering at Edith Cowan University, Australia. She received Ph.D. degree in the Western Australian School of Mines at Curtin University, Western Australia. She served as Principal Chair of international conference (e.g., the Chief Committee Chair of the Intelligent Technology for Power and Energy Conference 2025 in Amsterdam, Netherlands), the Editorial Board Members for peer-reviewed journals (e.g., Advances in Geo-Energy Research, International Journal of Coal Science & Technology, Scientific Reports, Advanced Light Materials, etc), the Editor of books and special issues, the invited keynote speaker of conferences, and the invited honorary consultant and guest lecturer in academia and industry. Her research mainly includes low-carbon energy and storage (e.g., carbon storage, underground hydrogen storage, natural hydrogen, shale gas/oil), with over 60 journal articles and book chapters published in the past seven ye