Diphosphorus pentasulfide is a chemical compound with the formula P2S5. It is a yellow solid that is insoluble in water. It is often used as a reagent in organic synthesis, particularly in the preparation of thiophosphoryl chloride, which is used in the production of organophosphorus compounds. Diphosphorus pentasulfide can also be used as a source of sulfur in various chemical reactions. It has a pungent odor and is toxic if ingested or inhaled.