Trimesic acid, also known as benzene-1,3,5-tricarboxylic acid, is an organic compound with the formula C<sub>6</sub>H<sub>3</sub>(CO<sub>2</sub>H)<sub>3</sub>. It is one of three isomers of benzenetricarboxylic acid. A colorless solid, trimesic acid has some commercial value as a precursor to some plasticizers.
Trimesic acid can be combined with para-hydroxypyridine to make a water-based gel, stable up to 95 ðC.
Trimesic acid crystallizes from water to form a hydrogen-bonded hydrated network with wide unidimensional empty channels.