The cranial base (also known as base of skull, skull base; latin: basis cranii) is the most inferior part of the skull forming the floor of the cranial cavity. The cranial base is formed by five bones: ethmoid, sphenoid, occipital, both frontal and both temporal bones.
The base of the skull can be inspected from two sides - from inside and outside. The inner aspect of the cranial base is known as the internal cranial base, and it is topographically divided further into three regions - anterior, middle and posterior cranial fossae. The outside of the cranial base is called the external cranial base.