The pulmonary veins are large blood vessels that receive oxygenated blood from the lungs and drain into the left atrium of the heart. There are four pulmonary veins, two from each lung. The pulmonary veins are among the few veins that carry oxygenated blood.

The pulmonary veins play an essential role in respiration, by receiving blood that has been oxygenated in the alveoli and returning it to the left atrium.