The rectus capitis posterior major muscle is a small, elongated muscle located in the back of the neck. It originates at the spinous process of the axis (second cervical vertebra) and inserts into the medial aspect of the occipital bone. The rectus capitis posterior major muscle is one of several muscles that make up the posterior cervical region.

The main function of the rectus capitis posterior major muscle is to extend the head at the atlanto-occipital joint (joint between the base of the skull and the first cervical vertebra). This movement is essential for activities such as looking upwards and nodding the head. The rectus capitis posterior major muscle also helps to laterally flex (bend to the side) the head and rotate the head to the opposite side.

In everyday life, the rectus capitis posterior major muscle is used in many activities that involve extension of the head, such as looking upwards or nodding the head. It is also used in activities that require lateral flexion and rotation of the head, such as turning to look behind you or shaking your head from side to side.