Hiram Winnett Orr (March 17, 1877 – October 11, 1956) was an American orthopedic surgeon who was born in Pennsylvania and was raised and lived the rest of his life in Nebraska. More than any other person, Orr was responsible for the invention of an effective method of using plaster casts and surgery to achieve a reduction in infection rates during treatment of open fractures and compound fractures before the widespread adoption of antibiotics.