The basilar artery is part of the blood supply system for the brain and central nervous system. It is formed where the two vertebral arteries join at the base of the skull.

The basilar artery carries oxygenated blood to the cerebellum, brainstem, and occipital lobes. The cerebellum helps with voluntary processes such as posture, balance, coordination, and speech. The brainstem plays a role in regulating several vital functions, including heart rate, eating, sleeping, and breathing. Visual processing takes place in the occipital lobes.

Several arteries branch from the basilar artery at the upper portion of the brainstem, delivering blood to various regions of the brain. Two posterior cerebral arteries lead to the temporal lobes (important for processing of sounds) and the outer layer of the occipital lobes. A pair of superior cerebellar arteries, another pair of anterior inferior cerebellar arteries, and several paramedian and circumferential pontine arteries also branch from the basilar artery. Cerebellar arteries supply the cerebellum and pontine arteries supply the pons, which relays information between different areas of the brain.

Interruption of the blood flow through the basilar artery can lead to severe brain damage, organ malfunction, or even death. An aneurysm, or bulge in the artery wall, may push that portion of the brain, causing rupture and hemorrhage (bleeding). A thrombosis, or blood clot, may block the artery and prevent blood from passing through. Because of its location, as well as the key role it plays in providing oxygen and nutrients to vital portions of the brain, an aneurysm or thrombosis in the basilar artery is particularly dangerous.