The monograph highlights the evolution of relations between the Danube principalities and Porta at the end of the XIV - the first third of the XVI century. in the context of international relations in the southeastern region, the objective prerequisites of the emerging relations of the Danube principalities with the Ottoman Empire and the nature of these relations are considered. The process of establishing the vassal dependence of the Wallachian and Moldavian principalities on the Port and the manifestation of the peculiarities of their position in the system of the Ottoman Empire is traced, the time of completion of this process for each of the principalities is determined. The study is based on an analysis of a wide range of sources - both published and archival.