Superfund sites are polluted places in the United States that need long-term cleanup of harmful materials. These sites include landfills, mines, factories, and processing plants where dangerous waste was not handled properly or thrown away. They were listed under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980. This law allowed the United States Environmental Protection Agency (EPA) to create a list of such locations, known as the National Priorities List (NPL).

The NPL helps the EPA decide which sites need more study for cleaning up the environment. 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 the list, and 457 sites have been cleaned up and removed from the list. New Jersey, California, and Pennsylvania have the most Superfund sites.