William Parry Murphy Sr. (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 anemia (specifically, pernicious anemia).

[citation needed] He discovered that ingesting large amounts of liver seemed to restore anemia more quickly of all foods.

[citation needed] The active ingredient in this case, found serendipitously, was not iron, but rather a water-soluble extract containing a new substance.

Even before the vitamin had been completely characterized, the knowledge that raw liver and its extracts treated pernicious anemia (previously a terminal disease) was a major advance in medicine.

[citation needed] Minot and Murphy's famous paper Treatment of pernicious anemia by a special diet was published in 1926.