2-Chloroethyl ethyl sulfide is the organosulfur compound with the formula C<sub>2</sub>H<sub>5</sub>SC<sub>2</sub>H<sub>4</sub>Cl. It is a colorless liquid. The compound is part of the family of vesicant compounds known as half mustards, has been heavily investigated because of its structural similarity to the sulfur mustard S(C<sub>2</sub>H<sub>4</sub>Cl)<sub>2</sub>. The of the half mustard is 252 mg/kg (oral, rats) compared to 2.4 mg/kg for the full mustard.