Psychedelic therapy refers to the proposed use of psychedelic drugs, such as psilocybin, MDMA, LSD, and ayahuasca, to treat mental disorders. As of 2021, psychedelic drugs are controlled substances in most countries and psychedelic therapy is not legally available outside clinical trials, with some exceptions.

Albert Hofmann was a Swiss chemist known for being the first to synthesize, ingest, and learn of the psychedelic effects of lysergic acid diethylamide (LSD). Hofmann's team also isolated, named and synthesized the principal psychedelic mushroom compounds psilocybin and psilocin. He authored more than 100 scientific articles and numerous books, including LSD: Mein Sorgenkind. In 2007, he shared first place with Tim Berners-Lee on a list of the 100 greatest living geniuses published by The Daily Telegraph newspaper.