French-American physician and physiologist who in 1956 shared the Nobel Prize for Physiology or Medicine with Dickinson W. Richards (Richards, Dickinson Woodruff) and Werner Forssmann (Forssmann, Werner) for discoveries concerning heart catheterization and circulatory changes.

His medical studies interrupted by World War I, Cournand graduated from the University of Paris in 1930. He studied at Bellevue Hospital, New York City, where he met Richards. Together they collaborated in clinical lung and heart research and perfected Forssmann's procedure, now termed cardiac catheterization, whereby a tube is passed into the heart from a vein at the elbow. With this procedure it became possible to study the functioning of the diseased human heart and to make more accurate diagnoses of the underlying anatomic defects. Cournand and Richards also used the catheter to examine the pulmonary artery, thus enabling improvement in the diagnosis of lung diseases as well.

Cournand joined the faculty of the College of Physicians and Surgeons of Columbia University in 1934, retiring as emeritus professor of medicine in 1964. He remained active as a special lecturer until his final illness. He became a naturalized citizen of the United States in 1941.