Mellitic anhydride, the anhydride of mellitic acid, is an organic compound with the formula C<sub>12</sub>O<sub>9</sub>.
Containing no other elements (e.g., hydrogen) besides carbon and oxygen, mellitic anhydride is an oxide of carbon (oxocarbon), and, along with CO<sub>2</sub>, CO, and C<sub>3</sub>O<sub>2</sub>, is one of the only four that are reasonably stable under standard conditions. It is a white sublimable solid, apparently obtained by Justus Liebig and Friedrich Wöhler in 1830 in their study of mellite ("honey stone") and has the empirical formula C<sub>4</sub>O<sub>3</sub>. The substance was properly characterized in 1913 by H. Meyer and K. Steiner. It retains the aromatic character of the benzene ring.