The splenius cervicis (also known as the splenius colli) is a paired long and relatively thin deep muscle of the back, which is located in the back of the neck. It stretches between the spinous processes of the thoracic vertebrae and transverse processes of the cervical vertebrae. Together with the splenius capitis, the splenius cervicis lie in the superficial layer of the deep back muscles.

Origin: spinous processes of the third to sixth thoracic vertebrae (T3 - T6).

Insertion: posterior tubercles of the transverse processes of the first to third cervical vertebrae (C1 - C3).

Action: bilateral contractions - extension of the neck; unilateral contractions - rotation and lateral flexion of the neck to the ipsilateral side.

Innervation: dorsal rami of the lower cervical spinal nerves that arise from the cervical plexus.

Blood supply: occipital artery of the external carotid artery, transverse cervical artery of the thyrocervical trunk and the deep cervical artery of the costocervical trunk.