Gallium(I) oxide, digallium monoxide or gallium suboxide is an inorganic compound with the formula Ga2O.

Gallium(I) oxide can be produced by reacting gallium(III) oxide with heated gallium in vacuum:[4] It can also be obtained by reacting gallium with carbon dioxide in vacuum at 850 °C.

[5] Gallium(I) oxide is a by-product in the production of gallium arsenide wafers:[6][7] Gallium(I) oxide is a brown-black diamagnetic solid which is resistant to further oxidation in dry air.

It starts decomposing upon heating at temperatures above 500 °C, and the decomposition rate depends on the atmosphere (vacuum, inert gas, air).

[4]