Archibald Joseph Cronin (19 July 1896 – 6 January 1981), known as A. J. Cronin, was a Scottish physician and novelist. His best-known novel is ''The Citadel'' (1937), about a Scottish physician who serves in a Welsh mining village before achieving success in London, where he becomes disillusioned about the venality and incompetence of some doctors. Cronin knew both areas, as a medical inspector of mines and as a physician in Harley Street. The book exposed unfairness and malpractice in British medicine and helped to inspire the National Health Service.