Oxirene is a heterocyclic chemical compound which contains an unsaturated three-membered ring containing two carbon atoms and one oxygen atom.

The molecule was synthesized in low temperature ices and detected upon sublimation by isomer selective photoionization reflectron time-of-flight mass spectrometry.

[2] Quantum chemical computational techniques found the configuration to be extremely strained and proposed an antiaromatic 4π electron system, as such oxirene is expected to be very high energy.

[3][4] Experimental indications exist that substituted oxirenes (as intermediates or transition states) may be involved in carbonylcarbene rearrangements observed in the Wolff rearrangement.

[5] Computational evidence also point to the intermediacy of oxirenes in the ozonolysis of alkynes.