Water contamination is a global issue with significant ecological, social, and economic consequences. This chapter examines the origins of water pollution, differentiating between natural and anthropogenic sources, and categorizes key pollutants, including organic, inorganic, microbiological, and emerging pollutants. It also explores their environmental pathways, persistence, and interactions within aquatic ecosystems. The ecological impacts of contamination are analysed, with emphasis on eutrophication, bioaccumulation, and biomagnification. These processes not only disrupt biodiversity and ecosystem services but also pose risks to human health through waterborne exposure and trophic transfer. Case studies illustrate how pollution sources and contaminant dynamics vary across different geographical and climatic contexts. Furthermore, the chapter discusses current challenges in water quality management, highlighting the role of monitoring strategies in pollution assessment and mitigation. Advances in real-time monitoring and predictive models offer new tools for tracking contamination trends, enabling more effective regulatory and remediation efforts. Ensuring the sustainability of water resources requires an integrated approach that combines scientific research, policy development, and technological innovation to address both existing and emerging threats to aquatic ecosystems.