2-(3-benzoyl-1-pyridinio)-3,4-dioxocyclobutenolate.

The title compound, C16H9NO4, also known as the 3-benzoylpyridinium betaine of squaric acid, exhibits a dipolar electronic ground-state structure with a positively charged pyridinium fragment and a negatively charged squarate moiety. In the molecule, the two aromatic rings are twisted by 56.03 (2) degrees relative to one another. The three-dimensional packing of the molecules is stabilized by C-H...O short contacts.