In chemistry, disulfate or pyrosulfate is the anion with the molecular formula . Disulfate is the IUPAC name. It has a dichromate-like structure and can be visualised as two corner-sharing SO<sub>4</sub> tetrahedra, with a bridging oxygen atom. In this anion, sulfur has an oxidation state of +6. Disulfate is the conjugate base of the hydrogen disulfate (hydrogen pyrosulfate) ion , which in turn is the conjugate base of disulfuric acid (pyrosulfuric acid).
Industrial production of sulfate ester-based surfactants involves the reaction (sulfation) of fatty alcohols with sulfur trioxide. For example, dodecyl alcohol is sulfated using sulfur trioxide. The reaction proceeds by initial formation of the pyrosulfate:
Several million tons are produced annually.