thumb|link=The Mysterious Affair at Styles is a detective novel by Agatha Christie. It was written in 1916 and was first published by John Lane in the United States in October 1920 and in the United Kingdom by The Bodley Head (John Lane's UK company) on 21 January 1921. The U.S. edition retailed at US $2.00 and the UK edition at seven shillings and sixpence (7/6).