The oculomotor nerve is the third cranial nerve. Arising from the midbrain, it passes through the superior orbital fissure to gain entry into the orbit. From here, it not only supplies the majority of the extraocular muscles but also carries with it parasympathetic innervation to the sphincter and ciliary muscles. Therefore, the oculomotor nerve is responsible not only for a wide variety of eye movements but also for pupillary constriction and lens accommodation. A variety of pathologies may affect this nerve, but it will result in ptosis, the eye rotated downward and outward and with a fixed, dilated pupil. A variety of simple bedside and advanced tests exist to fully assess the integrity of this nerve.