Phosphorus trichloride is a chemical compound of phosphorus and chlorine, having the chemical formula PCl₃. It has a trigonal pyramidal shape. It is the most important of the three phosphorus chlorides. It is an important industrial chemical, being used for the manufacture of organophosphorus compounds for a wide variety of applications. It has a ³¹P NMR signal at around +220 ppm with reference to a phosphoric acid standard.