Germanium monoxide (chemical formula GeO) is a chemical compound of germanium and oxygen. It can be prepared as a yellow sublimate at 1000 ðC by reacting GeO<sub>2</sub> with Ge metal. The yellow sublimate turns brown on heating to 650 ðC. GeO is not well characterised. It is amphoteric, dissolving in acids to form germanium(II) salts and in alkali to form "trihydroxogermanates" or "germanites" containing the Ge(OH)<sub>3</sub><sup>âÂÂ</sup> ion.
Germanium oxide decomposes to Ge and GeO<sub>2</sub>.