Tetraoxidane is an inorganic compound of hydrogen and oxygen with the chemical formula H2O4.

[4] The compound is prepared by a chemical reaction between hydroperoxyl radicals (HOO•) at low temperatures:[5][6] This is the fourth member of the polyoxidanes.

The first three are water [(mon)oxidane], hydrogen peroxide (dioxidane), and trioxidane.

The term "tetraoxidane" extends beyond the parent compound to several daughter compounds of the general formula R2O4, where R can be hydrogen, halogen atoms, or various inorganic and organic monovalent radicals.

The two Rs together can be replaced by a divalent radical, so heterocyclic tetraoxidanes also exist.