Skull is the bone structure that forms the head in most vertebrates. It supports facial structures and provides a protective cavity for the brain. The skull consists of two parts: the skull and the mandible. In humans, these two parts are nerve skull and visceral skull or facial bone, including the mandible as its largest bone. The skull forms the most anterior part of the skeleton and is the product of cranialization - the brain and some sensory structures, such as the eyes, ears, nose and mouth. In humans, these sensory structures are part of the facial skeleton.

The functions of the skull include protecting the brain, fixing the distance between the eyes to achieve stereo vision, and fixing the position of the ears to achieve sound positioning of sound direction and distance. In some animals, such as the horned ungulates, the skull also has a defensive function, that is, to provide a mounting (on the frontal bone) for the horn.

The English word "skull" can be derived from the ancient Nordic word "skull", while the Latin word "cranium" comes from the Greek root (kranion).

The skull is composed of many fused flat bones and contains many pores, pits, protrusions and some cavities or sinuses. In zoology, there are openings in the skull called fenestras.