Plutonium(III) oxide is an inorganic compound of plutonium and oxygen with the chemical formula . This is a sesquioxide of plutonium and is a lower oxide compared to the more common plutonium dioxide .
The cubic modification of the compound is formed by thermal dissociation of plutonium dioxide:
The hexagonal modification is formed during the reduction of plutonium dioxide with metallic plutonium:
The compound forms black crystals of cubic system, space group I a3.
The compound also forms crystals of hexagohal system, space group P 3m1.
The compound oxidizes when stored in open air: