Trimellitic anhydride is an organic compound with the formula HO<sub>2</sub>CC<sub>6</sub>H<sub>3</sub>(C<sub>2</sub>O<sub>3</sub>). It is the cyclic anhydride of trimellitic acid. The compound is a colorless to white solid. It's primarily used in the production of various polymers, polyesters, agricultural chemicals and dyes. Several thousand tons of this compound are produced annually as a precursor to plasticizers for polyvinyl chloride. It is produced by air-oxidation of 1,2,4-trimethylbenzene.