River pollution is a type of water pollution where the water within the river is contaminated. Water pollution occurs when harmful substances, such as chemicals or microorganisms, contaminate a stream, river, lake, ocean, aquifer, or other body of water, degrading water quality and making it unusable for drinking, cooking, cleaning, swimming, and other activities. Pollutants include chemicals, trash, bacteria, parasites, fertilizers, pesticides, pharmaceutical products, nitrates, phosphates, plastics, faecal waste, and even radioactive substances. All forms of pollution eventually make their way to water. Air pollution settles onto lakes and oceans, while land pollution can seep into an underground stream, then to a river, and finally to the ocean.

Water pollutants may cause disease or act as poisons. Bacteria and parasites in poorly treated sewage may enter drinking water supplies and cause digestive problems such as cholera and diarrhea. Hazardous chemicals, pesticides, and herbicides from industries, farms, homes, and golf courses can cause acute toxicity and immediate death, or chronic toxicity that can lead to neurological problems or cancers.

According to the Environmental Protection Agency, nearly half of our rivers and streams and more than one-third of our lakes are polluted and unfit for swimming, fishing, and drinking. Nutrient pollution, which includes nitrates and phosphates, is the leading type of contamination in these freshwater sources.