Chlorous acid is an inorganic compound with the formula HClO2.

HClO2 can be prepared through reaction of barium or lead chlorite and dilute sulfuric acid: Chlorous acid is a powerful oxidizing agent, although its tendency to undergo disproportionation counteracts its oxidizing potential.

[citation needed] Chlorine is the only halogen to form an isolable acid of formula HXO2.

[1] Fluorine is resistant to oxidation, having a -1 oxidation state even in hypofluorous acid, and is thus unable to form any higher oxoacids; despite the name, fluorite minerals are chemically fluoride compounds.

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