Europium(III) oxide (Eu2O3), is a chemical compound of europium and oxygen. It is widely used as a red or blue phosphor in television sets and fluorescent lamps, and as an activator for yttrium-based phosphors. It is also an agent for the manufacture of fluorescent glass. Europium fluorescence is used in the anti-counterfeiting phosphors in Euro banknotes.
Europium oxide has two common structures: Monoclinic (mS30, SpaceGroup = C2/m, No. 12) and cubic (cI80, SpaceGroup = Ia-3, No. 206). The cubic structure is similar to that of manganese(III) oxide.