Thiirene is an organosulfur compound with the formula C2H2S.

It can be viewed as a derivative of cyclopropene, but with the methylene group replaced by sulfur.

[1] No thiirene has been isolated at room temperature, but they have been observed spectroscopically at low temperatures.

[2] Thiirene-S-oxides and S-alkylthiirenium salts have been characterized by X-ray crystallography.

[3] This article about an organic compound is a stub.