Superfund sites are polluted areas in the United States that need long-term cleanup to remove harmful substances. These sites include landfills, mines, manufacturing facilities, and processing plants where toxic waste was not properly handled or disposed of. They were identified under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980. CERCLA allowed the United States Environmental Protection Agency (EPA) to create a list of these locations, which are added to the National Priorities List (NPL).

The NPL helps the EPA decide which sites need more study for environmental cleanup. As of June 6, 2024, there were 1,340 Superfund sites on the NPL in the United States. Thirty-nine more sites are being considered for addition to the list, and 457 sites have been cleaned up and removed from the list. New Jersey, California, and Pennsylvania have the highest number of Superfund sites.