Aorta, thoracic: The thoracic aorta is a section of the aorta, the largest artery in the body, within the chest. Specifically, the thoracic aorta is that part of the aorta that starts after the arch of the aorta and runs down to the diaphragm, the great muscle that separates the chest from the abdomen.

The thoracic aorta gives off numerous branches that supply oxygenated blood to the chest cage and the organs within the chest.

Like the other sections of the aorta (the ascending aorta, aortic arch and abdominal aorta), the thoracic aorta is an arbitrary anatomic entity. The aorta is one continuous conduit that stems from the left ventricle of the heart to carry blood to most of the body. The thoracic aorta is nonetheless a hallowed and convenient subdivision of the aorta.

The thoracic aorta is known in medical Latin variously as the aorta thoracica, the aorta thoracalis, and the pars thoracalis aortae (under which it is often concealed in print medical dictionaries).