Marine genomics is a vast field that encompasses various disciplines, reflecting the immense diversity of marine environments and the organisms that inhabit them. Given that the world's oceans cover 70% of the planet and are home to an estimated 2.2 million eukaryotic marine species, this diversity comes as no surprise. Marine genomics tackles a wide range of fundamental questions by employing cutting-edge genomic approaches tailored to marine species. This book explores these approaches, delving into topics such as evolutionary development in basal marine animals, population connectivity, adaptation to environmental change, and the integration of genomic data with functional concepts.The book provides comprehensive coverage of these topics, shedding light on the exciting discoveries enabled by genome-based research in marine (and freshwater) organisms. It emphasizes the significance of genomic approaches within the broader framework of environmental science, showcasing how genomic insights contribute to our understanding of marine ecosystems. The researchers and scholars from various disciplines, such as marine biology, genomics, evolutionary biology, environmental science, and related fields will find this book valuable. It appeals to individuals seeking a comprehensive overview of the current state of marine genomics and its applications. The book is valuable to both experts in the field who wish to deepen their understanding of specific topics and newcomers who seek an introduction to the subject. Its interdisciplinary nature makes it suitable for professionals interested in the intersection of genomics, ecology, and marine sciences.