The rhomboid major is a skeletal muscle of the back that connects the scapula with the vertebrae of the spinal column. It originates from the spinous processes of the thoracic vertebrae T2–T5 and supraspinous ligament; it inserts onto the lower portion of the medial border of the scapula. It acts together with the rhomboid minor to keep the scapula pressed against thoracic wall and to retract the scapula toward the vertebral column.

As the word rhomboid suggests, the rhomboid major is diamond-shaped. The major in its name indicates that it is the larger of the two rhomboids.^{[citation needed]}

The rhomboid major arises from the spinous processes of the thoracic vertebrae T2–T5 as well as the supraspinous ligament.

It inserts on the medial border of the scapula, from about the level of the scapular spine to the scapula's inferior angle.

The rhomboid major, like the rhomboid minor, is innervated by the ventral primary ramus via the dorsal scapular nerve (C5).

Both rhomboid muscles also derive their arterial blood supply from the dorsal scapular artery.

The rhomboid major is considered a superficial back muscle. It is deep to the trapezius, and situated directly inferior to the rhomboid minor.^{[citation needed]}

The two rhomboids are sometimes fused into a single muscle.