The United States federal Superfund law, officially the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), established the federal Superfund program, administered by the Environmental Protection Agency (EPA). The program is designed to investigate and clean up sites contaminated with hazardous substances. Sites managed under this program are referred to as "Superfund" sites. There are 40,000 federal Superfund sites across the country, and approximately 1,300 of those sites have been listed on the National Priorities List (NPL). Sites on the NPL are considered the most highly contaminated and undergo longer-term remedial investigation and remedial action (cleanups).

The EPA seeks to identify parties responsible for hazardous substances releases to the environment (polluters) and either compel them to clean up the sites, or it may undertake the cleanup on its own using the Superfund (a trust fund) and seek to recover those costs from the responsible parties through settlements or other legal means.

Approximately 70% of Superfund cleanup activities historically have been paid for by the potentially responsible parties (PRPs), the latter reflecting the polluter pays principle. However, 30% of the time the responsible party either cannot be found or is unable to pay for the cleanup. In these circumstances, taxpayers had been paying for the cleanup operations. Through the 1980s, most of the funding came from an excise tax on petroleum and chemical manufacturers. However, in 1995, Congress chose not to renew this tax and the burden of the cost was shifted to taxpayers. Since 2001, most of the cleanup of hazardous waste sites has been funded through taxpayers generally. Despite its name, the program suffered from under-funding, and by 2014 Superfund NPL cleanups had decreased to only 8 sites, out of over 1,200. In November 2021 Congress reauthorized an excise tax on chemical manufacturers.

The EPA and state agencies use the Hazard Ranking System (HRS) to calculate a site score (ranging from 0 to 100) based on the actual or potential release of hazardous substances from a site. A score of 28.5 places a site on the National Priorities List, eligible for long-term, remedial action (i.e., cleanup) under the Superfund program. As of March 23, 2022, there were 1,333 sites listed; an additional 448 had been delisted, and 43 new sites have been proposed.The Superfund law also authorizes federal natural resource agencies, primarily EPA, states and Native American tribes to recover natural resource damages caused by hazardous substances, though most states have and most often use their own versions of a state Superfund law. CERCLA created the Agency for Toxic Substances and Disease Registry (ATSDR).

The primary goal of a Superfund cleanup is to reduce the risks to human health through a combination of cleanup, engineered controls like caps and site restrictions such as groundwater use restrictions. A secondary goal is to return the site to productive use as a business, recreation or as a natural ecosystem. Identifying the intended reuse early in the cleanup often results in faster and less expensive cleanups. EPA's Superfund Redevelopment Program provides tools and support for site redevelopment.