In chemistry, carbonic acid is an inorganic compound with the chemical formula H₂CO₃. As a dilute solution in water, it is pervasive, but the pure compound, a colorless gas, can only be obtained.

The carbonic anhydrases (or carbonate dehydratases) form a family of enzymes that catalyze the interconversion between carbon dioxide and water and the dissociated ions of carbonic acid (i.e. bicarbonate and hydrogen ions).