This book covers various aspects of aquatic animal health, such as pathogenic and beneficial microbes, disease diagnosis, treatment and preventive measures, biosecurity, disease management. The environmental factors affecting aquatic animal well-being and their nutritional requirements are also discussed. Finally, emerging trends, and future research and management directions are also concluded in this book. Aquatic animals are a crucial source of nutrition for people worldwide, as they provide at least 20% of animal protein intake for over 3 billion individuals, according to the Food and Agriculture Organization (FAO). Furthermore, fishing and aquaculture industries generate employment and income for millions, particularly in developing countries. However, pollution, habitat destruction, overfishing, climate change, and disease outbreaks pose a threat to aquatic animal health. Disease outbreaks and pathogenic microbes can cause significant harm, necessitating immediate attention. Addressing this issue requires multifaceted approach that includes enhancing water quality, managing animal stress levels, improving biosecurity measures, and practicing responsible aquaculture techniques. Finally, collaboration between government, industry, and researchers is critical to developing new and effective strategies for mitigating the impact of disease outbreaks on aquatic animal health. This book provides concise information for students, teachers, researchers, and academicians interested in the field of aquatic animal health. It also serves as a reference book to administrators, practitioners, stakeholders, and non-professionals interested in sustainable aquatic animal health management.