Mescaline or 3,4,5-trimethoxyphenethylamine is a psychedelic hallucinogenic drug and entheogen of the phenethylamine family. It is ether synthesized or extracted from the peyote cactus (Lophophora williamsii), the San Pedro cactus (Trichocereus pachanoi), or the Peruvian Torch (Trichocereus peruvianus).

It was first isolated and identified in 1897 by the German Arthur Heffter and first synthesized in 1919. The effective dosage is 200 - 400 mg (3.75 mg/kg) with the effects lasting for up to twelve hours. It is not physically addictive. In the US it was made illegal in 1970 by the Comprehensive Drug Abuse Prevention and Control Act. Extract from peyote was used in religious ceremonies from the earliest human contact, notably by the Huichols in Mexico.