Project MKUltra was an illegal human experiments program designed and undertaken by the U.S. Central Intelligence Agency (CIA) to develop procedures and identify drugs that could be used during interrogations to weaken people and force confessions through brainwashing and psychological torture. It began in 1953 and was halted in 1973. MKUltra used numerous methods to manipulate its subjects' mental states and brain functions, such as the covert administration of high doses of psychoactive drugs (especially LSD) and other chemicals without the subjects' consent, electroshocks, hypnosis, sensory deprivation, isolation, verbal and sexual abuse, and other forms of torture.

MKUltra was preceded by Project Artichoke. It was organized through the CIA's Office of Scientific Intelligence and coordinated with the United States Army Biological Warfare Laboratories. The program engaged in illegal activities, including the use of U.S. and Canadian citizens as unwitting test subjects. MKUltra's scope was broad, with activities carried out under the guise of research at more than 80 institutions aside from the military, including colleges and universities, hospitals, prisons, and pharmaceutical companies. The CIA operated using front organizations, although some top officials at these institutions were aware of the CIA's involvement.

MKUltra was revealed to the public in 1975 by the Church Committee of the United States Congress and Gerald Ford's United States President's Commission on CIA activities within the United States (the Rockefeller Commission). Investigative efforts were hampered by CIA Director Richard Helms's order that all MKUltra files be destroyed in 1973; the Church Committee and Rockefeller Commission investigations relied on the sworn testimony of direct participants and on the small number of documents that survived Helms's order. In 1977, a Freedom of Information Act request uncovered a cache of 20,000 documents relating to MKUltra, which led to Senate hearings. Some surviving information about MKUltra was declassified in 2001.