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William Parry Murphy (Stoughton, Wisconsin, February 6, 1892 – October 9, 1987) was an American physician who shared the Nobel Prize in Physiology or Medicine in 1934 with George Richards Minot and George Hoyt Whipple for their combined work in devising and treating macrocytic anaemia.

Murphy was born on February 6, 1892, at Stoughton, Wisconsin. He was educated at the public schools of Wisconsin and Oregon. He completed his A.B. degree in 1914 from the University of Oregon. He completed his M.D. in 1922 from Harvard Medical School.

In 1924, Murphy bled dogs to make them anemic, and then fed them various substances and gauged their improvement. He discovered that ingesting large amounts of liver seemed to cure the disease. Minot and Whipple then set about to chemically isolate the curative substance and ultimately were able to isolate vitamin B12 from the liver.

Murphy married Pearl Harriett Adams on September 10, 1919. They had a son, Dr. William P. Murphy Jr., and a daughter, Priscilla Adams.