This special issue addresses practices of border-making and their consequences on the territory of the former Austro-Hungarian Monarchy. As the reality did not correspond to the peaceful Europe articulated in the Paris Treaties, a multitude of (un)foreseen complications followed the drawing of borders and states. Articles include new case studies on the creation, centralization or peripheralization of border regions, such as Subcarpathian Rus, Vojvodina, Banat and the Carpathian Mountains, on border zones such as the Czechoslovakian harbour in Germany, and on cross-border activities. The special issue shows how disputes over national identities and ethnic minorities, as well as other factors such as the economic consequences of the new state borders, appeared on the interwar political agenda and coloured the lives of borderland inhabitants. Adopting a bottom-up approach, the contributions demonstrate the agency of borderlands and their people in the establishment, functioning, disorganization or ultimate breakdown of some of the newly created interwar nation-states.