Sydnone imine is a mesoionic heterocyclic aromatic chemical compound. Sydnone imine is the imine of sydnone where the keto functional group of sydnone (=O) has been replaced with an imine (=NH) group.

A variety of pharmaceutical drugs include sydnone imines in their chemical structure including feprosidnine, linsidomine, mesocarb, and molsidomine, among others.

In sydnone imines, both the negative and the positive charges are delocalized within the ring and the imine group.