The splenius cervicis (also known as splenius colli) is a deep muscle of the back, which is located in the back of the neck.

• Origin: spinous processes of the third to sixth thoracic vertebrae (T3 - T6).
• Insertion: transverse process of the atlas (C1), tip of the transverse process of the axis (C2), and into the posterior tubercle of the third cervical vertebra (C3).
• Action: rotation and lateral flexion of the head when acting unilaterally; extends the head when acting on both sides (bilaterally).
• Innervation: lateral branches of the dorsal rami of the lower cervical spinal nerves that arise from the cervical plexus.