Kermesic acid is an anthraquinone derivative and the main component of the red dye kermes (false carmine). The compound is the aglycone of carminic acid, the main component of true carmine. As a dye, it is known as Natural Red 3.

Kermesic acid, like carminic acid and the laccaic acids, is an insect dye obtained from scale insects. Kermesic acid is found in insects of the genus Kermes. It is the only colored component of the dye kermes.

The chemical structure of kermesic acid was elucidated by Otto Dimroth in 1916.