Gallic acid is a colorless or slightly yellow crystalline compound obtained from nutgalls. It is used in photography, pharmaceuticals, and as an analytical reagent. Gallic acid is an odorless white solid. Sinks in water. Gallic acid is found in a number of land plants, such as the parasitic plant, Cynomorium coccineum, the aquatic plant, Myriophyllum spicatum, and the blue-green alga, Microcystis aeruginosa. Gallic acid is found both free and as part of hydrolyzable tannins.

Gallic acid is formed from 3-dehydroshikimate by the action of the enzyme shikimate dehydrogenase to produce 3,5-didehydroshikimate. This latter compound tautomerizes to form the redox equivalent gallic acid, where the equilibrium lies essentially entirely toward gallic acid because of the coincidentally occurring aromatization.