2-Ethyl-imidazolium terephthalate.

The asymmetric unit of the title compound, C(5)H(9)N(2) (+)·C(8)H(5)O(4) (-), consists of one protonated 2-ethyl-imidazolium cation and two half terephthalate anions. The anions and cations are linked through N-H⋯O hydrogen bonds while the anions are associated via O-H⋯O inter-actions, resulting in a layered structure. The ethyl group of the cation is disordered over twosites of occupancies 0.812†(14) and 0.188†(14). The hydroxy H atoms of the anions are equally disordered over two symmetry-related sites.