This book, Microplastics and Nanoplastics in Aquatic Environments, provides a comprehensive and multidisciplinary overview of the growing threat posed by microplastics and nanoplastics in aquatic ecosystems, a global issue attracting increasing attention from the scientific community, regulatory authorities, and the general public. The ubiquitous presence of these particles and their effects, both ecological and on the health of organisms, are complex and often underestimated. The volume explores the ecotoxicological impacts of micro- and nanoplastics, showing how they can interfere with the fundamental biological processes of aquatic organisms. It also examines interactions between these particles and other chemical or biological contaminants, which can amplify overall toxicity and pose a significant threat to biodiversity and ecosystem stability. The book’s interdisciplinary approach integrates biological, chemical, and ethical perspectives, offering reflection on the human role in the plastic crisis, collective responsibility towards aquatic ecosystems, and the production and consumption choices that have led to the current situation. It provides conceptual tools and up-to-date scientific insights useful for researchers, students, and professionals in environmental science and public health, supporting the development of effective mitigation and management strategies. By combining ecology, toxicology, chemistry, environmental policy, and ethics, the book serves as a valuable resource for understanding the complexity of microplastics and nanoplastics and for promoting innovative, sustainable solutions.