Dimethyl disulfide (DMDS) is an organic chemical compound with the molecular formula CH3SSCH3. It is a flammable liquid with an unpleasant, odor. The compound is colorless although impure samples often appear yellowish.

This product is a presulfiding agent for steam cracking, the process that turns hydrocarbons into ethylene and propylene, which is used for olefin-based products. DMS is added to the feedstock to reduce coke and carbon monoxide formation during the high-temperature thermal cracking of hydrocarbons in the tubular reactors. The deposition of coke on the boundary layer can significantly affect the run length, yields, and the coil life of a pyrolysis furnace. In addition, carbon monoxide is a poison for downstream catalysts. DMS acts as an efficient H2S precursor, which allows for H2S to form at the metal interface. The sulfur is absorbed to inhibit reactions.