4-Acetoxy-N,N-dimethyltryptamine (also known as 4-AcO-DMT, 4-Acetoxy-DMTO-Acetylpsilocin, and psilacetin) is a novel psychedelic substance of the tryptamine class. It is chemically similar to psilocybin, the active ingredient in psilocybin mushrooms (magic mushrooms). It belongs to a group known as the substituted tryptamines which act by stimulating serotonin receptorsin the brain.

The synthesis of 4-AcO-DMT was first reported in 1963 by Albert Hofmann and Franz Troxler. However, its properties were not examined and no further studies were carried out. A 1999 paper by David E. Nichols suggested it as a useful alternative to psilocybin for pharmacological research. Reports of human use began to surface following its appearance on the online research chemical market in the 2010s.