Entheogens include a variety of substances referred to as hallucinogens, psychedelics, and sacred plants. Entheogen reflects the perspectives embodied in traditions around the world, where they are seen as having intrinsic spiritual properties and intelligence. Entheogens include many substances that alter experience in dramatic ways which are interpreted as sacred, evoking experiences of direct contact with a supernatural or spiritual domain, including special relationships with spiritual beings, often plant or animal deities. Entheogens have shamanic uses, and have been noted for their ability to provoke the personal experience of transformation into an animal. They are used in a variety of rituals, where they are viewed as essential to a community’s contact with sacred and mythological realities, and promote social solidarity by reinforcing interpersonal relations among members of the community. There is also abundant evidence of prehistoric entheogen use in complex pre-modern cultures. Entheogens continue to be a source of religious traditions in the modern world, most notably in the ayahuasca traditions of South American which combine MAO-inhibiting Banisteriopsis species to make available the N,N-Dimethyltryptamine (DMT) from other plants. The intrinsic power of the entheogens to induce religious experiences and extreme alterations of consciousness illustrates and explains their primordial association with shamanism and mystical traditions worldwide.