Lanthanum oxide is most useful as a precursor to other lanthanum compounds. Neither the oxide nor any of the derived materials enjoys substantial commercial value, unlike some of the other lanthanides. Many reports describe efforts toward practical applications of La₂O₃, as described below.

La₂O₃ forms glasses of high density, refractive index, and hardness. Together with oxides of tungsten, tantalum, and thorium, La₂O₃ improves the resistance of the glass to attack by alkali. La₂O₃ is an ingredient in some piezoelectric and thermoelectric materials.

La₂O₃ has been examined for the oxidative coupling of methane.