The neopallium in the mammallian brain is all of the cerebral hemisphere except the rhinencephalon and the corpus striatum. The neopallium includes gray matter on the sulci and gyri of the cerebral cortex and the associated long white fibers.

The neopallium is phylogenically younger than cerebral structures arising from paleopallium or archipallium. The neocortical area is significantly more developed in porportion to other parts of the brain in Old World monkeys and in humans than in older species.