In my thesis I examine Thrace as a geographical unity during the Ottoman conquest in the fourteenth century. In the first chapter I present the sources that I used, Byzantine and Ottoman. The life and works of the chronographers are discussed to the extent that they assist us in comprehending their ideology and mentality. I focus on the contemporary sources of the fourteenth century. The second chapter treats with the diplomatic relations between the Byzantines and the Turks in the fourteenth century before and after the Turkish settlement in Thrace. This provides the reader the base to figure the political situation, which facilitated the Turkish expansion in Thrace. The central part of my thesis is a topographic analysis of Thrace during the Ottoman expansion. I tried to research the etymology of the Thracian toponyms and then attempted to locate them on a map, mentioning their Byzantine and modern Turkish, Greek or Bulgarian equivalents, if possible. This visualizes the routes that the Ottomans followed when conquering Thrace. A map of fourteenthcentury Thrace accompanies my thesis. The fourteenth century was of paramount importance for both the Byzantine Empire and the Ottoman Emirate. In Byzantine history it marks the end of a great medieval empire, especially relating to its administrative and economic decadence. For Ottoman history, it punctuates the transition of a frontier beglik into a world-dominant empire. Thrace was the first European territory of the Ottomans and functioned as the vaulting horse of their expeditions in the Balkans. The intellectual intercourse of Greek-Orthodox and Turco-Islamic political ideology gave birth to the heir of the Byzantine State.