The Hazardous Materials Transportation Act (HMTA), enacted in 1975, is the principal federal law in the United States regulating the transportation of hazardous materials. Its purpose is to "protect against the risks to life, property, and the environment that are inherent in the transportation of hazardous material in intrastate, interstate, and foreign commerce" under the authority of the United States Secretary of Transportation.

The Act was passed as a means to improve the uniformity of existing regulations for transporting hazardous materials and to prevent spills and illegal dumping endangering the public and the environment, a problem exacerbated by uncoordinated and fragmented regulations. Regulations are enforced through four key provisions encompassing federal standards under Title 49 of the United States Code:

Violation of the HMTA regulations can result in civil or criminal penalties, unless a special permit is granted under the discretion of the Secretary of Transportation.

In the 1970s, landfills throughout the United States began to refuse the acceptance of hazardous wastes for the protection of property, the environment, and liability from what would later become known as Superfund sites, which dramatically increased the cost of disposal. The high cost of disposal led to increased dumping of materials that were increasingly being deemed "hazardous" by the public and government. Illegal dumping took place on vacant lots, along highways, or on the actual highways themselves. At the same time, increased accidents and incidents with hazardous materials during transportation was a growing problem, causing damage to property and the environment, injury, and death. At the time, the U.S. Department of Transportation estimated that 75% of all hazardous waste shipments violated existing regulations due to a lack of inspection personnel and poor coordination among the U.S. Coast Guard, the Federal Aviation Administration, the Federal Highway Administration, and the Federal Railroad Administration. The increasing frequency of illegal "midnight" dumping and spills, along with the already existing inconsistent regulations and fragmented enforcement, led to the passing of the Hazardous Materials Transportation Act. It was signed into law on January 3, 1975 by President Gerald Ford, as a means to strengthen the Hazardous Materials Transportation Control Act of 1970 and unify existing regulations.

Since its passage, the HMTA has had two major amendments:

It is estimated that the United States alone makes over 500,000 shipments of hazardous materials every day. More than 90% of these shipments are transported by truck, and anywhere from 5–15% of those trucks are carrying hazardous materials regulated under the HMTA. Approximately 50% of those materials are corrosive or flammable petroleum products, while the remaining shipments represent any of the 2,700 other chemicals considered hazardous in interstate commerce. Accidents that occurred in the transportation of hazardous materials resulted in injury, death, and the destruction of property and the environment. However, the accidents were not limited to the road. The number of incidents regarding hazardous wastes was second in railway accidents behind road accidents. The passage of the HMTA (and its subsequent amendments) has significantly reduced the number of incidents and the gravity of those incidents with hazardous materials in transportation.

The HMTA is one of the eight laws defining the EPA's Emergency Management Program. The other laws comprising the Emergency Management Program include the Clean Air Act (CAA), the Clean Water Act (CWA), the Oil Pollution Act (OPA), the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), Superfund Amendments and Reauthorization Act (SARA), the Emergency Planning and Community Right-to-Know Act (EPCRA), and the Chemical Safety Information, Site Security and Fuels Regulatory Relief Act (CSISSFRRA).

The primary objective of the HMTA is to protect "life, property, and the environment" from the inherent risks of transporting hazardous material, in all major modes of commerce, by improving the regulation and enforcement authority of the Secretary of Transportation. It is in the Secretary's authority to designate material or a group or class of material as hazardous when they meet the definition of hazardous material under the Act.