The rhomboid muscles are a pair of muscles located in the upper back. They include the rhomboid major and rhomboid minor muscles. The rhomboid major originates at the spinous processes of the thoracic vertebrae, and inserts into the medial border of the scapula (shoulder blade). The rhomboid minor originates at the nuchal ligament and the spinous process of the seventh cervical vertebra, and inserts into the medial border of the scapula just below the rhomboid major.

The main function of the rhomboid muscles is to retract the scapulae (pull the shoulder blades together) and downwardly rotate them. This movement is essential for activities such as squeezing the shoulder blades together or shrugging the shoulders, and helps to provide stability and support for the shoulder joint. The rhomboid muscles also help to elevate the scapulae, and assist in upward rotation of the scapulae. They are also used in activities that require stability and support for the shoulder joint, such as carrying a heavy backpack or pushing a heavy object.