Gold(III) oxide (Au<sub>2</sub>O<sub>3</sub>) is an inorganic compound of gold and oxygen with the formula Au<sub>2</sub>O<sub>3</sub>. It is a red-brown solid that decomposes at 298 ðC.
According to X-ray crystallography, AuO features square planar gold centers with both 2- and 3-coordinated oxides. The four Au-O bond distances range from 193 to 207 picometers.
The crystals can be prepared by heating amorphous hydrated gold(III) oxide with perchloric acid and an alkali metal perchlorate in a sealed quartz tube at a temperature of around 250 ðC and a pressure of around 30 MPa.