N-Methylmorpholine N-oxide (more correctly 4-methylmorpholine 4-oxide), NMO or NMMO is an organic compound. This heterocyclic amine oxide and morpholine derivative is used in organic chemistry as a co-oxidant and sacrificial catalyst in oxidation reactions for instance in osmium tetroxide oxidations and the Sharpless asymmetric dihydroxylation or oxidations with TPAP.[1] NMO is commercially supplied both as a monohydrate C5H11NO2·H2O and as the anhydrous compound. The monohydrate is used as a solvent for cellulose in the Lyocell process to produce cellulose fibers.