Psychonautics (from the Ancient Greek ψυχή psychē 'soul, spirit, mind' and ναύτης naútēs 'sailor, navigator') refers both to a methodology for describing and explaining the subjective effects of altered states of consciousness, including those induced by meditation or mind-altering substances, and to a research group in which the researcher voluntarily immerses themself in an altered mental state in order to explore the accompanying experiences.

The term has been applied diversely, to cover all activities by which altered states are induced and utilized for spiritual purposes or the exploration of the human condition, including shamanism, lamas of the Tibetan Buddhist tradition, the Siddhars of Ancient India, sensory deprivation, and archaic/modern drug users who use entheogenic substances in order to gain deeper insights and spiritual experiences. Self-experimentation of psychedelics in groups may foster innovation of alternative medication treatment. A person who uses altered states for such exploration is known as a psychonaut.

The term psychonautics derives from the prior term psychonaut, which began appearing in North American works in the late 1950s. The first reference that corresponds to contemporary usages of the term was in the 1965 edition of the Group Psychotherapy journal. A 1968 magazine, Beyond Baroque, refers to Timothy Leary as a psychonaut.^{[citation needed]}

German author Ernst Jünger describes ideas related to psychonautics - in reference to Arthur Heffter - in his 1970 essay on his own extensive drug experiences Annäherungen: Drogen und Rausch (literally: "Approaches: Drugs and Inebriation"). In this essay, Jünger draws many parallels between drug experience and physical exploration—for example, the danger of encountering hidden "reefs."

Peter J. Carroll made Psychonaut the title of a 1982 book on the experimental use of meditation, ritual and drugs in the experimental exploration of consciousness and of psychic phenomena, or "chaos magic".

The term's first published use in a scholarly context is attributed to ethnobotanist Jonathan Ott, in 2001.

Clinical psychiatrist Jan Dirk Blom describes psychonautics as denoting "the exploration of the psyche by means of techniques such as lucid dreaming, brainwave entrainment, sensory deprivation, and the use of hallucinogens or entheogens, and a psychonaut as one who "seeks to investigate their mind using intentionally induced altered states of consciousness" for spiritual, scientific, or research purposes.

Psychologist Dr. Elliot Cohen of Leeds Beckett University and the UK Institute of Psychosomanautics defines psychonautics as "the means to study and explore consciousness (including the unconscious) and altered states of consciousness; it rests on the realization that to study consciousness is to transform it." He associates it with a long tradition of historical cultures worldwide. Leeds Beckett University offers a module in Psychonautics and may be the only university in the UK to do so.^{[citation needed]}