This article aims at a better understanding of the changing nature of borders in warring Syria. Contrary to much media commentary, the Syrian uprising and the subsequent conflict have not been about territorial claims. In 2011, the borders of Syria were de facto pacified and, with the important exception of the border with Israel, were accepted as the legitimate boundaries of the Syrian state. This, however, does not contradict the fact that the unfolding of the Syrian uprising has had deep transformative effects on the borders of the country. Their nature, functions and management have significantly evolved since the uprising first broke out. In 2017, these borders no longer delineate a coherent territory under the control of a unique and somehow cohesive actor: the state. The ongoing territorial and political fragmentation of the country into territories controlled by different armed parties has given rise to multiple forms of control over the Syrian border that reflect the outcome of the armed confrontation. This article analyses the transformations of the borders from the outer boundaries of a state that exercises its sovereignty over its territory and delivers state functions and public goods to its citizens to a spatial envelope in which competing internal legitimacies operate. It also explores the new dynamics of the borders in relation with Syria’s neighbours and the international order.