Cerebral hypoxia refers to deprivation of oxygen supply to brain tissue. Mild or moderate cerebral hypoxia is sometimes known as diffuse cerebral hypoxia. It can cause confusion and fainting, but its effects are reversible. Total deprivation of oxygen to the brain is called cerebral anoxia. Extended periods of cerebral hypoxia can lead to brain death or permanent brain damage.

Most cases of cerebral hypoxia are caused by a sudden change in brain oxygen levels. The body can normally respond to mild gradual changes in blood oxygen with little or no noticeable effect on brain function. The acclimatization process used by high altitude climbers is an example of such adjustment.

The presence of cerebral hypoxia symptoms indicates that the brain has been overwhelmed by a change in its oxygen supply. Consequently, even mild symptoms of cerebral hypoxia require immediate medical attention.