The third cranial nerve which is responsible for the nerve supply to the muscles around the eye, including the upper eyelid muscle, which raises the eyelid; the extraocular muscle, which moves the eye inward; and the pupillary muscle, which constricts the pupil.

Paralysis of the oculomotor nerve results in a drooping eyelid (ptosis), deviation of the eyeball outward (and therefore double vision), and a dilated (wide-open) pupil.