Rapid industrialization and urban growth in recent years have led to the widespread presence of emerging contaminants in water, posing significant threats to environmental sustainability and human health. Over 80% of global wastewater is discharged untreated, introducing contaminants such as metals, microbes, pesticides, and pharmaceuticals into ecosystems. In industrial areas, heavy metals often exceed permissible limits by 50–100 times, whereas persistent organic pollutants (POPs) contribute to 1.5 million deaths annually due to long-term exposure. This chapter explores the types, characteristics, and hazards of emerging contaminants, emphasizing the need for advanced treatment technologies, stronger regulations, and interdisciplinary collaboration. Serving as a resource for academia, industry, and policymakers, this chapter urges a global, coordinated effort to mitigate these challenges and ensure sustainable water resources for future generations.