A skull fracture is a break in one or more of the eight bones that form the cranial portion of the skull, usually occurring as a result of blunt force trauma. If the force of the impact is excessive, the bone may fracture at or near the site of the impact and cause damage to the underlying structures within the skull such as the membranes, blood vessels, and brain.

While an uncomplicated skull fracture can occur without associated physical or neurological damage and is in itself usually not clinically significant, a fracture in healthy bone indicates that a substantial amount of force has been applied and increases the possibility of associated injury. Any significant blow to the head results in a concussion, with or without loss of consciousness.

A fracture in conjunction with an overlying laceration that tears the epidermis and the meninges, or runs through the paranasal sinuses and the middle ear structures, bringing the outside environment into contact with the cranial cavity is called a compound fracture. Compound fractures can either be clean or contaminated.

There are four major types of skull fractures: linear, depressed, diastatic, and basilar. Linear fractures are the most common, and usually require no intervention for the fracture itself. Depressed fractures are usually comminuted, with broken portions of bone displaced inward—and may require surgical intervention to repair underlying tissue damage. Diastatic fractures widen the sutures of the skull and usually affect children under three. Basilar fractures are in the bones at the base of the skull.

Linear skull fractures are breaks in the bone that transverse the full thickness of the skull from the outer to inner table. They are usually fairly straight with no bone displacement. The common cause of injury is blunt force trauma where the impact energy transferred over a wide area of the skull.^{[citation needed]}

Linear skull fractures are usually of little clinical significance unless they parallel in close proximity or transverse a suture, or they involve a venous sinus groove or vascular channel. The resulting complications may include suture diastasis, venous sinus thrombosis, and epidural hematoma. In young children, although rare, the possibility exists of developing a growing skull fracture especially if the fracture occurs in the parietal bone.

A depressed skull fracture is a type of fracture usually resulting from blunt force trauma, such as getting struck with a hammer, rock or getting kicked in the head. These types of fractures—which occur in 11% of severe head injuries—are comminuted fractures in which broken bones displace inward. Depressed skull fractures present a high risk of increased pressure on the brain, or a hemorrhage to the brain that crushes the delicate tissue.^{[citation needed]}

Compound depressed skull fractures occur when there is a laceration over the fracture, putting the internal cranial cavity in contact with the outside environment, increasing the risk of contamination and infection. In complex depressed fractures, the dura mater is torn. Depressed skull fractures may require surgery to lift the bones off the brain if they are pressing on it by making burr holes on the adjacent normal skull.