4-Ethyl-amino-3-nitro-benzoic acid.

In the title compound, C(9)H(10)N(2)O(4), an intra-molecular N-H⋯O hydrogen-bond inter-action generates an S(6) ring motif. The nitro group is slightly twisted away from its attached benzene ring [dihedral angle = 15.29 (15)°]. In the crystal structure, mol-ecules are stacked down the a axis caused by short O⋯O(-1-x, -y, 2-z) contacts of 2.6481 (16) Å involving the O atoms of the nitro groups. The crystal packing is consolidated by inter-molecular O-H⋯O hydrogen bonds, linking the mol-ecules into centrosymmetric dimers.