Carbon monosulfide is a chemical compound with the formula CS. This diatomic molecule is the sulfur analogue of carbon monoxide, and is unstable as a solid or a liquid, but it has been observed as a gas both in the laboratory and in the interstellar medium. The molecule resembles carbon monoxide with a triple bond between carbon and sulfur. The molecule is not intrinsically unstable, but it tends to polymerize. This tendency reflects the greater stability of C-S single bonds.