Thiosalicylic acid is an organosulfur compound containing carboxyl and sulfhydryl functional groups.

[3] Thiosalicylic acid can be prepared from anthranilic acid via diazotization followed by the addition of sodium sulfide and then reduction with zinc.

[4] Thiosalicylic acid is a precursor to the dyestuff thioindigo.

It is a precursor to drug candidates for treatment of atherosclerosis and melanoma.

[5][6] The preservative benzisothiazolinone is prepared from thiosalicylic acid.