Manganese(II) oxide is an inorganic compound with chemical formula MnO.

Like many monoxides, MnO adopts the rock salt structure, where cations and anions are both octahedrally coordinated.

[3] MnO has the distinction of being one of the first compounds[4] to have its magnetic structure determined by neutron diffraction, the report appearing in 1951.

[7] MnO can also be prepared by heating the carbonate:[8] This calcining process is conducted anaerobically, lest Mn2O3 form.

Other uses include: a catalyst in the manufacture of allyl alcohol, ceramics, paints, colored glass, bleaching tallow and textile printing.