8-Chloro-4-oxo-4H-chromene-3-carbaldehyde.

In the title compound, C10H5ClO3, a chlorinated 3-formyl-chromone derivative, all atoms are essentially coplanar (r.m.s. deviation = 0.032†à for the non-H atoms), with the largest deviation from the least-squares plane [0.0598†(14)†à ] being for a pyran-ring C atom. In the crystal, mol-ecules are linked through stacking inter-actions along the b axis [shortest centroid-centroid distance between the pyran and benzene rings = 3.566†(2)†à ].