Chloric acid, HClO3, is an oxoacid of chlorine, and the formal precursor of chlorate salts.

Chloric acid is thermodynamically unstable with respect to disproportionation.

Chloric acid is stable in cold aqueous solution up to a concentration of approximately 30%, and solution of up to 40% can be prepared by careful evaporation under reduced pressure.

Above these concentrations, chloric acid solutions decompose to give a variety of products, for example: Chloric acid is a powerful oxidizing agent.

[citation needed] It may be produced from barium chlorate through its reaction with sulfuric acid, which results in a solution of chloric acid and insoluble barium sulfate precipitate:[2] The chlorate must be dissolved in boiling water and the acid should be somewhat diluted in water and heated before mixing.