3-Methoxytyramine (3-MT), also known as 3-methoxy-4-hydroxyphenethylamine, is a metabolite of the neurotransmitter dopamine formed by the introduction of a methyl group to dopamine by the enzyme catechol-O-methyl transferase (COMT). 3-MT can be further metabolized by the enzyme monoamine oxidase (MAO) to form homovanillic acid (HVA), which is then typically excreted in the urine. Originally thought to be physiologically inactive, 3-MT has recently been shown to act as an agonist of human TAAR1.