The title of this chapter was not chosen lightly. It brings two highly controversial terms together in a novel combination and, in so doing, attempts to call attention to a specific phenomenon in contemporary religion, namely the religious use of psychoactive substances as means of access to spiritual insights about the true nature of reality. The question of why, and in what sense(s), this type of religion should be understood as a form of “esotericism” will be addressed below; but something must be said at the outset about the adjective “entheogenic” and its implications. The substantive entheogen was coined in 1979 by a group of ethnobotanists and scholars of mythology who were concerned with finding a terminology that would acknowledge the ritual use of psychoactive plants reported from a variety of traditional religious contexts, while avoiding the questionable meanings and connotations of current terms, notably “hallucinogens” and “psychedelics”. As suggested by its roots in Greek etymology (ȅνθ∊ος), natural or artificial substances can be called entheogens (adjective: entheogenic) if they generate, or bring about, unusual states of consciousness in which those who use them are believed to be “filled”, “possessed” or “inspired” by some kind of divine entity, presence or force. While the altered states in question are pharmacologically induced, such religious interpretations of them are obviously products of culture.