The internal granular layer of the cortex, also commonly referred to as the granular layer of the cortex, is the layer IV in the subdivision of the mammalian cortex into 6 layers. The adjective internal is used in opposition to the external granular layer of the cortex.
The external granular layer of the cerebral cortex is commonly known as layer II. It should not be confused with the internal granular layer of the cerebral cortex (commonly known as layer IV).