The disappearance of the Habsburg and Ottoman Empires and the territorial changes after the wars of 1912–1918 still raise the question of their legacy in the countries of Southeastern Europe after the end of the First World War. One of the dimensions of this problem relates to the legacy of the two Empires to the rail networks in this region after the Great War. The main purpose of this article is to present the process of building and sharing the various railway lines that form the rail networks of Bulgaria, Greece, Romania and the Kingdom of Serbs, Croats and Slovenes (RSCS) after 1918. This subject covers the initial period of establishment as well as the subsequent development of railways in the Balkans and surrounding areas. The research deals mainly with the railway history of the Habsburg Empire (from 1867 - Austria-Hungary) and more specifically the networks of Austria (Cisleithanie), Hungary (Transleithanie) and Bosnia-Herzegovina (after 1878). Particular attention is given to the three provinces of the Austro-Hungarian Empire: Croatia-Slavonia, Dalmatia and Bosnia-Herzegovina, taking into account provinces and regions such as the Austrian Coast (Küstenland), Batchka, Banat, Transylvania and Bucovina. In addition, the presentation will deal with the Ottoman Empire and more specifically with European Turkey, with the exception of the vassal provinces. The text is divided into three parts which cover the main stages of railway construction and the distribution of the railway networks in the region envisaged between 1830 and 1919/20: a) period 1830–1878; b) period 1878–1912; c) period 1913–1919 / 20.