Trimethylsulfonium chloride is a chemical compound with the formula C3H9ClS. It consists of a central sulfur atom bonded to three methyl groups and a chloride ion. This compound is often used in organic synthesis and as a reagent in various chemical reactions. In its solid form, trimethylsulfonium chloride appears as a white crystalline powder. It is soluble in water and polar solvents, making it useful in laboratory settings. Due to its properties, it can serve as a source of the trimethylsulfonium ion, which is important in the synthesis of other organic compounds.