The National Highway Traffic Safety Administration (NHTSA) is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes."

As part of its activities, NHTSA is charged with writing and enforcing Federal Motor Vehicle Safety Standards as well as regulations for motor vehicle theft resistance and fuel economy, the latter under the rubric of the Corporate Average Fuel Economy (CAFE) system. NHTSA also licenses vehicle manufacturers and importers, allows or blocks the import of vehicles and safety-regulated vehicle parts, administers the vehicle identification number (VIN) system, develops the anthropomorphic dummies used in safety testing, as well as the test protocols themselves, and provides vehicle insurance cost information. The agency has asserted preemptive regulatory authority over greenhouse gas emissions, but this has been disputed by such state regulatory agencies as the California Air Resources Board.

Another of NHTSA's major activities is the creation and maintenance of the data files maintained by the National Center for Statistics and Analysis. In particular, the Fatality Analysis Reporting System (FARS), has become a resource for traffic safety research not only in the United States, but throughout the world. Research contributions using FARS by researchers from many countries appear in many non-U.S. technical publications, and provide a significant database and knowledge bank on the subject. Even with this database, conclusive analysis of crash causes often remains difficult and controversial, with experts debating the veracity and statistical validity of results.