Behentrimonium chloride, also known as docosyltrimethylammonium chloride or BTAC-228, is a yellow waxlike organic compound with chemical formula CH3(CH2)21N(Cl)(CH3)3, used as an antistatic agent and, sometimes, a disinfectant. It is commonly found in cosmetics such as conditioners, hair dye, and mousse, and also in detergents. In water treatment, it acts as an algaecide.