Ethyl xanthic acid is an organic compound with the chemical formula CH3CH2−O−C(=S)−SH.

It can be viewed as an O-ethyl ester of dithiocarbonic O,S-acid (the formula of that acid is S=C(OH)(SH)).

Ethyl xanthic acid belongs to the category of thioacids, where the prefix thio- means that an oxygen atom in the compound is replaced by a sulfur atom.

In aqueous solution, it decomposes rapidly by a unimolecular pathway to give carbon disulfide and ethanol.

[6] Ethyl xanthic acid reacts with water or moisture producing carbon disulfide.