A dicarbonate, also known as a pyrocarbonate, is a chemical containing the divalent  or  functional group, which consists of two carbonate groups sharing an oxygen atom. These compounds can be viewed as derivatives of the hypothetical compound dicarbonic acid,  or . Two important organic compounds containing this group are dimethyl dicarbonate  and di-tert-butyl dicarbonate .
It is one of the oxocarbon anions, consisting solely of oxygen and carbon. The anion has the formula  or . Dicarbonate salts are apparently unstable at ambient conditions, but can be made under pressure and may have a fleeting existence in carbonate solutions.
The term dicarbonate is sometimes used erroneously to refer to bicarbonate, the common name of the hydrogencarbonate anion  or esters of the hydrogencarbonate functional group . It is also sometimes used for chemicals that contain two carbonate units in their covalent structure or stoichiometric formula.