The cranial base is the most inferior part of the skull forming the floor of the cranial cavity.

It is formed by five bones:

• Ethmoid bone
• Sphenoid bone
• Occipital bone
• Frontal bones 
• Temporal bones (2)

The outside of the cranial base is called the external cranial base. The inner aspect of the skull base is known as the internal cranial base, and it is topographically divided into three regions:

• Anterior cranial fossa
• Middle cranial fossa
• Posterior cranial fossa