Francis Peyton Rous, American pathologist and virologist, Nobel Prize laureate (d. 1970)
Francis Peyton Rous () (October 5, 1879 – February 16, 1970) was an American pathologist at the Rockefeller University known for his works in oncoviruses, blood transfusion and physiology of digestion. A medical graduate from the Johns Hopkins University, he was discouraged to become a practicing physician due to severe tuberculosis. After three years of working as an instructor of pathology at the University of Michigan, he became dedicated researcher at the Rockefeller Institute for Medical Research for the rest of his career.

His discovery in 1911 that a chicken tumor was caused by a virus (later named Rous sarcoma virus) led to more discoveries and understanding of the role of viruses in the development of certain types of cancer. He was awarded a Nobel Prize in Physiology or Medicine for his work in 1966, 55 years after his initial discovery and he remains the oldest recipient of the Nobel Prize in Medicine or Physiology.He and Joseph R. Turner studied methods to make use of blood types for blood transfusion. During World War I, they developed a technique for preserving blood sample by using citrate. This enabled the first practical storage of blood samples for transfusion and was introduced by Oswald H. Robertson at the front line in Belgium in 1917 as the world's first blood bank.