5-Chloro-1H-indole-3-carb­oxy­lic acid

In the title compound, C₉H₆ClNO₂, the carboxyl group is twisted from the indole ring system by 9.00 (8)°. In the crystal, inversion dimers linked by pairs of O—H...O hydrogen bonds generate R₂²(8) loops and N—H...O hydrogen bonds link the dimers into (001) sheets. Aromatic π–π stacking inter­actions [centroid–centroid distance = 3.7185 (12) A °] are also observed.