Mescaline is a psychedelic hallucinogen obtained from the small, spineless cactus Peyote (Lophophora williamsi), the San Pedro cactus, Peruvian torch cactus, and other mescaline-containing cacti. It is also found in certain members of the Fabaceae (bean family) and can be produced synthetically.

People have used hallucinogens for hundreds of year, mostly for religious rituals or ceremonies. Mescaline leads to rich, intense visual hallucinations. From the earliest recorded time, peyote has been used by natives in northern Mexico and the southwestern United States, where it grows, as a part of traditional religious rites. It has an effect that is similar to LSD or psilocybin (magic mushrooms) and other hallucinogenic drugs.