2-Hydroxy-1,4-benzoxazin-3-one monooxygenase (, BX5 (gene), CYP71C3 (gene)) is an enzyme with systematic name 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one,NAD(P)H:oxygen oxidoreductase (N-hydroxylating). This enzyme catalyses the following chemical reaction
2-Hydroxy-1,4-benzoxazin-3-one monooxygenase is involved in the biosynthesis of protective and allelopathic benzoxazinoids in some plants.