The title compound, C(16)H(10)O(5), consists of two isobenzofuran-1(3H)-one moieties which are linked by a bridging O atom. The two halves of the mol-ecule display approximate non-crystallographic mirror symmetry. The dihedral angle between the two isobenzofuran-1(3H)-one ring systems is 53.18 (6) Å. Two chiral carbon centres are observed in the compound, but their absolute configurations could not be determined. In the crystal structure, inter-molecular C-H⋯O hydrogen bonds link mol-ecules into zigzag chains along c. Additional C-H⋯O inter-actions connect adjacent chains.