Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia, dating back to the Early Jurassic. They are the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the inside of their lower teeth. The teeth wore unevenly with chewing and developed sharp ridges that allowed neornithischians to break down tougher plant food than other dinosaurs.
They died out in the Cretaceous-Paleogene Extinction Event.