A hydroxybenzoquinone (formula: C6H4O3) is any of several organic compounds that can be viewed as derivatives of a benzoquinone through replacement of one hydrogen atom (H) by a hydroxyl group (-OH).
In general, the term may mean any benzoquinone derivative where any number n of hydrogens have been replaced by n hydroxyls, so that the formula is C6H4O2+n.
In this case the number n (which is between 1 and 4) is indicated by a multiplier prefix (mono-, di-, tri-, tetra-, penta-, or hexa-).
The IUPAC nomenclature uses dihydrobenzenedione instead of "benzoquinone", with the necessary prefixes to indicate the positions of the carbonyl oxygens (=O) — as in 2,3-dihydroxy-1a,4a-dihydrobenzene-1,4-dione (= 2,3-dihydroxy-1,4-benzoquinone).
The hydroxybenzoquinones (in the particular or the general sense) include many biologically and industrially important compounds, and are a building block of many medicinal drugs.