The War on Drugs is a prohibition campaign undertaken by the United States government with the assistance of participating countries, intended to reduce the illegal drug trade – to curb supply and diminish demand for specific psychoactive substances deemed immoral, harmful, dangerous, or undesirable. This initiative includes a set of laws and policies that are intended to discourage the production, distribution, and consumption of targeted substances. The term was first used by President Richard Nixon in 1969, and his choice of words was probably based on the War on Poverty, announced by President Lyndon B. Johnson in 1964.

On May 13, 2009, Gil Kerlikowske, the current Director of the Office of National Drug Control Policy, signaled that the Obama Administration would no longer use the term "War on Drugs," as he claims it is counter-productive and is contrary to the policy favoring treatment over incarceration in trying to reduce drug use.