Lutetium(III) chloride or lutetium trichloride is the chemical compound composed of lutetium and chlorine with the formula LuCl3. It forms hygroscopic white monoclinic crystals[1] and also a hydroscopic hexahydrate LuCl3·6H2O.[6] Anhydrous lutetium(III) chloride has the YCl3 (AlCl3) layer structure with octahedral lutetium ions.[7]