Carbon subsulfide is an organic, sulfur-containing chemical compound with the formula C3S2 and structure S=C=C=C=S.

This deep red liquid is immiscible with water but soluble in organic solvents.

Later, infrared and Raman spectroscopy showed that the structure is symmetrical with a D∞h point group symmetry,[3] i.e. S=C=C=C=S.

This treatment produced a black solution that after filtration and evaporation gave a cherry-red liquid.

Later preparations of C3S2 include thermolysis of a stream of CS2 in a quartz tube heated to 900 to 1100 °C as well as flash vacuum pyrolysis (FVP) of 1,2-dithiole-3-thiones.