Trichocereus macrogonus, synonym Echinopsis macrogonus, is a species of cactus found in Ecuador, Peru and Bolivia. Two varieties are accepted as of September 2023: var. macrogonus and var. pachanoi. Plants contain varying amounts of the psychoactive alkaloid mescaline. They have been used both ritually and in traditional medicine from pre-Columbian times. Trichocereus macrogonus is one of a number of similar species that may be called San Pedro cactus. Indigenous names include achuma and huachuma, although these too may be applied to similar species.

Trichocereus macrogonus var. pachanoi is a fast-growing columnar cactus found in the Andes at 2,000–3,000 m (6,600–9,800 ft) in altitude. It is one of a number of kinds of cacti known as San Pedro cactus. It is native to Ecuador, Peru and Colombia, but also found in Argentina, Bolivia, Chile and Venezuela and cultivated in other parts of the world. Uses for it include traditional medicine and traditional veterinary medicine, and it is widely grown as an ornamental cactus. It has been used for healing and religious divination in the Andes Mountains region for over 3,000 years.