Phosphorus oxide can refer to:
Phosphorus pentoxide (phosphorus(V) oxide, phosphoric anhydride), P2O5
Phosphorus trioxide (phosphorus(III) oxide, phosphorous anhydride), P2O3
Several other, less common, oxides of phosphorus, including P4O7, P4O8, P4O9, PO and P2O6
Phosphorus monoxide
Diphosphorus tetroxide