Formic Acid (also called methanoic acid) is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings.

A major use of Formic Acid is as a preservative and antibacterial agent in livestock feed. It is applied on fresh hay or other silage to promote the fermentation of lactic acid and to suppress the formation of butyric acid; it also allows fermentation to occur quickly, and at a lower temperature, reducing the loss of nutritional value. Formic Acid arrests certain decay processes and causes the feed to retain its nutritive value longer, and so it is widely used to preserve winter feed for cattle.

In the poultry industry, it is sometimes added to feed to kill bacteria. It is also used in the production of textiles and leather because of its acidic nature. It is also used as a coagulant in the production of rubber.

Formic acid is also used in place of mineral acids for various cleaning products, such as limescale remover and toilet bowl cleaner. Some formate esters are artificial flavorings or perfumes.

Beekeepers use formic acid as a miticide against the tracheal mite (Acarapis woodi) and the Varroa mite.