An arsonic acid is an organic compound that has the functional group −AsO(OH)2. They are the arsenic analogues of phosphonic acids. Salts and esters of arsonic acids are called arsonates.
The parent compound HAsO(OH)2 "arsonic acid" has not been found to exist. The tautomer As(OH)3, arsenous acid, is more stable.
The most important type of arsonic acids are phenylarsonic acids, which were used as pesticides and antiparasitics until the 21st century.
