This book provides an overview of aquatic toxicology, including mechanisms of toxicological responses and factors influencing toxicokinetics and toxicodynamics in aquatic organisms. It also discusses ecotoxicology and risk assessment, covering principles, toxicity testing methods, environmental monitoring, and biomonitoring techniques. The book aims to equip researchers, students, and policymakers with knowledge to address challenges posed by chemical contaminants in aquatic environments. By understanding aquatic toxicology, we can contribute to the preservation and conservation of these valuable ecosystems. This resource aims to be valuable for all individuals passionate about the health of aquatic ecosystems.