The posterior scalene (also posterior scalene muscle, latin: musculus scalenus posterior) is a muscle located in the lateral part of the neck. It is the smallest of the scalene muscles and situated most profoundly.
The posterior scalene originates from the posterior tubercles of the transverse processes of the 5th to 7th cervical vertebrae (C5 - C7), and inserts onto the outer surface of the second rib.
By contracting on both sides the posterior scalene flexes the neck forward. By contracting on one side it bends neck laterally. The posterior scalene lifts the second rib.
The posterior scalene is innervated by the anterior rami of the 5th to 7th cervical spinal nerves (C5 - C7).