The National Pollutant Discharge Elimination System  (NPDES) permit program addresses water pollution by regulating point sources that discharge pollutants to waters of the United States.

The NPDES permit program was created in 1972 by the Clean Water Act, the NPDES program is authorized to state governments by Environmental Protection Agency (EPA) to perform many permitting, administrative, and enforcement aspects of the program.

The Clean Water Act prohibits anybody from discharging "pollutants" through a "point source" into a "water of the United States" unless they have an NPDES permit. The permit will contain limits on what you can discharge, monitoring and reporting requirements, and other provisions to ensure that the discharge does not hurt water quality or people's health. In essence, the permit translates general requirements of the Clean Water Act into specific provisions tailored to the operations of each person discharging pollutants.