Water pollution is the contamination of water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water pollution results when contaminants mix with these water bodies. Contaminants can come from one of four main sources. These are sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Water pollution may affect either surface water or groundwater. This form of pollution can lead to many problems. One is the degradation of aquatic ecosystems. Another is spreading water-borne diseases when people use polluted water for drinking or irrigation. Water pollution also reduces the ecosystem services such as drinking water provided by the water resource.

जल प्रदूषण का मुख्य कारण मानव या जानवरों की जैविक या फिर औद्योगिक क्रियाओं के फलस्वरूप पैदा हुये प्रदूषकों को बिना किसी समुचित उपचार के सीधे जल धारायों में विसर्जित कर दिया जाता है। जल में विभिन्न प्रकार के हानिकारक पदार्थों के मिलने से जल प्रदूषण होता है।