Sir William Osler, 1st Baronet (July 12, 1849 – December 29, 1919) was a Canadian physician. He was one of the "Big Four" founding professors at Johns Hopkins Hospital as the first Professor of Medicine and founder of the Medical Service there. (The "Big Four" were William Osler, Professor of Medicine; William Stewart Halsted, Professor of Surgery; Howard A. Kelly, Professor of Gynecology; and William H. Welch, Professor of Pathology.) Osler created the first residency program for specialty training of physicians, and he was the first to bring medical students out of the lecture hall for bedside clinical training.
He has been called the "Father of modern medicine." Osler was a multifaceted physician and individual, functioning as a pathologist, internist, educator, bibliophile, historian, author, and renowned practical joker.