Methoxyamine is the organic compound with the formula CH₃ONH₂. Also called O-methylhydroxylamine, it is a colourless volatile liquid that is soluble in polar organic solvent and in water. It is a derivative of hydroxylamine with the hydroxyl hydrogen replaced by a methyl group, an alkoxyamine. Alternatively, it can be viewed as a derivative of methanol with the hydroxyl hydrogen replaced by an amino group. It is an isomer of N-methylhydroxylamine and aminomethanol.

Methoxyamine is prepared via O-alkylation of hydroxylamine derivatives. For example, it is obtained by O-methylation of acetone oxime followed by hydrolysis of the O-methylated oxime:

The other broad method involves methanolysis of hydroxylamine sulfonates:

Commercial products are usually the hydrochloride salt.

Analogous to the behavior of hydroxylamine, methoxyamine condenses with ketones and aldehydes to give imines.

Methoxyamine is used as a synthon for NH₂⁺. It undergoes deprotonation by methyl lithium to give CH₃ONHLi. This N-lithio derivative is attacked by organolithium compounds to give, after hydrolysis, amines:

Methoxyamine has potential medicinal uses. It covalently binds to apurinic/apyrimidinic (AP) DNA damage sites and inhibits base excision repair (BER), which may result in an increase in DNA strand breaks and apoptosis.This agent may potentiate the anti-tumor activity of alkylating agents.

Examples of drugs incorporating the methoxyamine unit are brasofensine and gemifloxacin.