2,6-Naphthalenedicarboxylic acid is an organic compound with the formula C<sub>10</sub>H<sub>6</sub>(CO<sub>2</sub>H)<sub>2</sub>. This colorless solid is one of several isomers of naphthalenedicarboxylic acid. It is a precursor to the high performance polyester polyethylene naphthalate (PEN, poly(ethylene-2,6-naphthalene dicarboxylate)). It is also used in the synthesis of some metal-organic frameworks.
It was first prepared by Robert Evert and in 1876 by hydrolysis of 2,6-dicyanonaphthalene.
1,8-Naphthalenedicarboxylic acid can be isomerized to 2,6-naphthalenedicarboxylic acid via the intermediacy of the dipotassium dicarboxylates. It is also produced by oxidation of 2,6-diisopropylnaphthalene.