Iodous acid is the chemical compound with the formula HIO2.

Its salts are named iodites; these are exceedingly unstable and have been observed but never isolated.

[1] They will rapidly disproportionate to molecular iodine and iodates.

Iodous acid is part of a series of oxyacids in which iodine can assume oxidation states of −1, +1, +3, +5, or +7.

A number of neutral iodine oxides are also known.