Germanium monoxide (chemical formula GeO) is a chemical compound of germanium and oxygen.

It can be prepared as a yellow sublimate at 1000 °C by reacting GeO2 with Ge metal.

The yellow sublimate turns brown on heating to 650 °C.

[1] It is amphoteric, dissolving in acids to form germanium(II) salts and in alkali to form "trihydroxogermanates" or "germanites" containing the Ge(OH)3− ion.

[2] Germanium oxide decomposes to Ge and GeO2.