thumb|link=The Mystery of the Blue Train is a work of detective fiction by Agatha Christie and first published in the United Kingdom by William Collins & Sons on 29 March 1928 and in the United States by Dodd, Mead and Company later in the same year. The UK edition retailed at seven shillings and sixpence (7/6) and the US edition at $2.00. The book features her detective Hercule Poirot.