The median nerve is a nerve that runs down the arm and forearm. It is one of the five main nerves originating from the brachial plexus.

The median nerve is formed from parts of the medial and lateral cords, and continues down the arm. It enters the forearm (with the brachial artery) and innervates most of the flexors in the forearm. It does not innervate flexor carpi ulnaris or the medial two digits of flexor digitorum profundus, which are supplied by the ulnar nerve.

The median supplies the muscles in the thenar eminence of the hand by a recurrent thenar branch, and the lateral two lumbrical muscles. The rest of the intrinsic muscles of the hand are supplied by the ulnar nerve.

In terms of sensory information, the median nerve cutaneously innervates the palmar side of the thumb, the index and middle finger, and half the ring finger. It also receives information from the nail bed of these fingers. The proximal part of the palm is supplied by a palmar branch, which leaves the nerve proximal to the wrist creases.

The median nerve is the only nerve that passes through the carpal tunnel, so it plays a large part in carpal tunnel syndrome.