The rectus capitis posterior major is a muscle that arises from the spinous process of the axis, which is the second cervical vertebra of the spine. The spinous process is a part of the vertebra that sticks out toward the back of the body. Also called the rectus capitis posticus major, the rectus capitis posterior major is located at the back of the neck where it significantly broadens as it rises into the bottommost part of the skull.

Functionally, the muscle works to promote certain head movements. Together with other structures within the neck — such as bones, joints, and muscles (like the rectus capitis posterior minor) — it extends and rotates the head. In terms of head movements, extending means moving the head backwards and rotating is turning the head.

A connection of soft tissues also exists from the muscle to the internal membrane lining the vertebrae. This connection plays a role in the tension among the neck muscles.

The blood supply to the muscle is provided by the vertebral and occipital arteries, while the nerve supply is provided by the suboccipital nerve.

Because of its location, the rectus capitis posterior major muscle may be severely affected by whiplash injury and vehicular collisions. The muscle may also be susceptible to strains, ruptures, tears, lacerations, contusions, infections, and certain neuromuscular diseases.