P-toluenesulfonyl isocyanate (PTSI) is a monoisocyanate commonly used as a dehydrating agent in industrial products.

It reacts with water to produce carbon dioxide and toluene sulfonamide, the latter of which generally does not react with alkyl isocyanates or aryl isocyanates and is soluble in ordinary solvents.

It can be used as a stabilizer for sealants.