Wilfred Gordon "Bill" Bigelow OC FRSC (June 18, 1913 – March 27, 2005) was a Canadian heart surgeon known for his role in developing the artificial pacemaker and the use of hypothermia in open heart surgery. In the 1950s, Bigelow developed the idea of using hypothermia as a medical procedure. This involves reducing a patient's body temperature prior to an operation in order to reduce the amount of oxygen needed, making heart operations safer. He wrote two books, Cold Hearts and Mysterious Heparin. He served as a director of the Audubon Society and the Nature Conservancy of Canada.