The infraspinatus (also infraspinatus muscle, latin: musculus infraspinatus) is a flat, triangular shaped muscle of the shoulder girdle.
The infraspinatus muscle originates from the walls of the infraspinous fossa on the posterior surface of the scapula. It completely fills the infraspinous fossa of the scapula. The muscle fibers of the infraspinatus travel laterally and insert onto the greater tubercle of the humerus.
The infraspinatus is one of the rotator cuff muscles that stabilizes the shoulder and provides external rotation of the upper arm.