The cranium, a portion of the skull commonly referred to as the braincase, describes the hard, skeletal structure of the head and face. The bones of the cranium possess distinctive features that allow easy identification of their position and orientation in the body. The human adult mandible, or lower jaw, is not generally considered by anatomists to be a part of the cranium.

The adult human cranium consists of 22 bones: 14 facial bones and 8 cranial bones. The cranial bones are the parietals, located at the top and sides of the skull, two temporal bones above the ears, the ethmoid around the nose, the sphenoid at the base of the skull, the frontal over the forehead, and the occipital. The occipital bone at the back of the skull forms a complex joint with the first vertebra of the neck (atlas) that permits nodding and rotation of the head.

At birth, the cranial bones are still forming and skull joints are soft and flexible. This allows the baby's head to compress and easily pass through the birth canal. The so-called "soft spots" on an infant's skull are termed as fontanels, areas where the bones of the cranium do not meet. Cranial bones fuse together in dovetailed, immovable joints called sutures, which make the skull rigid. By age two, the bones become mostly fused, but full fusion often does not occur until late in puberty.

Rare conditions such as Osteitis Deformans and Acromegaly can cause the bones of the skull to grow larger than normal. Falls, blows to the head and others accidents can cause the skull bones to crack and break. Skull fractures can be serious due to the proximity to neural tissue in the brain or the subsequent swelling of membranes (e.g., meningeal membranes) covering the central nervous system tissue.