In enzymology, a senecionine N-oxygenase () is an enzyme that catalyzes the chemical reaction
The 4 substrates of this enzyme are senecionine, NADPH, H<sup>+</sup>, and O<sub>2</sub>, whereas its 3 products are senecionine N-oxide, NADP<sup>+</sup>, and H<sub>2</sub>O.
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O<sub>2</sub> as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O<sub>2</sub> with NADH or NADPH as one donor, and incorporation of one atom o oxygen into the other donor. The systematic name of this enzyme class is senecionine,NADPH:oxygen oxidoreductase (N-oxide-forming). Other names in common use include senecionine monooxygenase (N-oxide-forming) and SNO.