In the title compound, C9H6O2, the carb-oxy-lic acid group is almost in the plane of the benzene ring, making a dihedral angle of 2.49 (18)°. In the crystal, mol-ecules are linked by pairs of O-H⋯O hydrogen bonds, forming classical acid-acid inversion dimers, with an R 2 (2)(8) ring motif. The dimers are linked by pairs of C-H⋯O hydrogen bonds forming chains, enclosing R 2 (2)(16) ring motifs, propagating along the c-axis direction.
Keywords: 3-ethynylbenzoic acid; crystal structure; hydrogen bonding.