Chloroethylene oxide is the organic compound with the formula ClC2H3O.

It is the epoxide of vinyl chloride.

The compound is rarely observed, but it is widely proposed as a metabolite of vinyl chloride, formed by the action of cytochrome-P450.

It is significant because it causes DNA alkylation.

It isomerizes to chloroacetaldehyde, which modifies adenosine residues by conversion to 1,N6-ethenodeoxyadenosine (εdA).