Which cranial nerve is the longest in the human body?

The vagus nerve is the longest cranial nerve in the human body.

The vagus nerve is cranial nerve X, or the tenth cranial nerve. It begins in the medulla oblongata of the brainstem and travels through the neck and thorax into the abdomen. Its extensive route gives it connections with the heart, lungs, digestive tract, and other organs.

The name vagus comes from Latin for “wandering,” reflecting its long, branching path. It carries both sensory and motor information and is a major part of the parasympathetic nervous system, which supports functions such as resting heart activity and digestion.

A common misunderstanding is that “cranial” means a nerve must remain inside the skull. Cranial nerves originate from the brain or brainstem, but some leave the skull and extend far into the body. The vagus nerve is especially distinctive because it reaches well beyond the head and neck.