Psilocin, an aromatic compound, sometimes also (mis)spelled psilocine, psilocyn, or psilotsin, is a psychedelic  mushroom alkaloid. It is found in most psychedelic mushrooms together with its phosphorylated counterpart psilocybin. Psilocin is a Schedule I drug under the Convention on Psychotropic Substances.The mind altering effects of psilocin are highly variable and subjective. The effects typically last anywhere from 3 to 8 hours depending on certain variables (such as metabolism, food interaction), however the effects can seem to last much longer due to psilocin's ability to distort the perception of time.

Psilocin can be obtained by dephosphorylation of natural psilocybin under strongly acidic or under alkaline conditions (hydrolysis). Another synthetic route uses the Speeter-Anthony tryptamine synthesis starting from 4-hydroxyindole.