The clavicle is a doubly curved short bone that connects the arm (upper limb) to the body (trunk), located directly above the first rib. It acts as a strut to keep the scapula in position so the arm can hang freely. Medially, it articulates with the manubrium of the sternum (breast-bone) at the sternoclavicular joint. At its lateral end it articulates with the acromion of the scapula (shoulder blade) at the acromioclavicular joint. It has a rounded medial end and a flattened lateral end.

From the roughly pyramidal sternal end, each clavicle curves laterally and anteriorly for roughly half its length. It then forms a smooth posterior curve to articulate with a process of the scapula (acromion). The flat, acromial end of the clavicle is broader than the sternal end. The acromial end has a rough inferior surface that bears prominent lines and tubercles. These surface features are attachment sites for muscles and ligaments of the shoulder.

The collarbone, also called the clavicle, is the bone over the top of your chest, between your breastbone (sternum) and shoulder blade (scapula). It is easy to feel the clavicle, because unlike other bones which are covered with muscle, only skin covers a large part of the bone. Clavicle fractures are extremely common. Broken collarbones occur in babies (usually during birth), children and adolescents (because the clavicle does not completely ossify, or develop, until the late teens), athletes (because of the risks of being hit or falling), or during many types of accidents and falls.[citation needed]

The clavicle serves several functions:

Even though it is classified as a long bone, the clavicle has no medullary (bone marrow) cavity like other long bones. It is made up of spongy (cancellous) bone with a shell of compact bone. It is a dermal bone derived from elements originally attached to the skull.

Muscles and ligaments that attach to the clavicle include:

The levator claviculae muscle, present in 2–3% of people, originates on the transverse processes of the upper cervical vertebrae and is inserted in the lateral half of the clavicle.

The clavicle is the first bone to begin the process of ossification (laying down of minerals onto a preformed matrix) during development of the embryo, during the 5th and 6th weeks of gestation. However, it is one of the last bones to finish ossification, at about 21-25 years of age. It forms by intramembranous ossification. It consists of a mass of cancellous bone surrounded by a compact bone shell. The cancellous bone forms via two ossification centres, one medial and one lateral, which fuse later on. The compact forms as the layer of fascia covering the bone stimulates the ossification of adjacent tissue. The resulting compact bone is known as a periosteal collar.

The clavicle varies more in shape than most other long bones. Occasionally, the clavicle is pierced by a branch of the supraclavicular nerve. The clavicle is thicker and more curved in manual workers, and the sites of muscular attachments are more marked. The right clavicle is usually stronger and shorter than the left clavicle.

The clavicle first appears as part of the skeleton in primitive bony fish, where it is associated with the pectoral fin; they also have a bone called the cleithrum. In such fish, the paired clavicles run behind and below the gills on each side, and are joined by a solid symphysis on the fish's underside. They are, however, absent in cartilagenous fish and in the vast majority of living bony fish, including all of the teleosts.