3-Methoxytyramine (3-MT), also known as 3-methoxy-4-hydroxyphenethylamine, is a human trace amine and the major metabolite of the monoamine neurotransmitter dopamine.

[1][2] It is formed by the introduction of a methyl group to dopamine by the enzyme catechol-O-methyltransferase (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.

3-Methoxytyramine occurs naturally in the prickly pear cactus (genus Opuntia),[3] and is in general widespread throughout the Cactaceae.

[1] Originally thought to be physiologically inactive, 3-MT was subsequently found to act as an agonist of the rodent and human TAAR1.