In the title compound, C(8)H(7)ClO(2), the hydroxyl and aldehyde groups are co-planar with the benzene ring [maximum deviation 0.018 (3) Å], and the Cl-C-C plane is almost perpendicular to the benzene ring [dihedral angle 83.7 (2)°]. An intra-molecular O-H⋯O hydrogen bond occurs between the hydroxyl and aldehyde groups.