The territory of Ostrog was inhabited many years before the spread of Christianity to the area. In the vicinity of the Zeta river paths carved the landscape in all directions to connect scattered Montenegro villages. Today, remnants of these paths dating back to roman times are still visible in the Povija area leading to a small fortress called Viris. The mild, rich Zeta river contributed to the quick settlement into the valley in early days of Montenegro. During the early Middle Ages the Ostrog Region was bordering the Herzegovina state Zahumlje. Other fortifications such as Budos (build by the Herzegovina state) and Susjed and of course Ostrog are also located in the area.

The exact date when the fortification of Ostrog was build, or the town of Ostrog located there today, is not known. In the middle of the XV century, in writings from 1441, it is documented that Ostrog was a boarder town of the Duke Stephan Vukcic Kosace, who was a local leader and landowner. Because of its boarder location as well as territorial clashes between the states on this territory, the town was always in the center of events. The exact location of the original fortification of Ostrog is believed to be a nearby ruin called Gradac, not very far away from Perucice. It is believed that following the arrival of the Turks in the late XV century the town was devastated and fell into ruin which is the reason the exact location of Kastrum (the original name of the town) is unknown. The building of the Monastery Ostrog put this important location in Montenegro cultural heritage back on the map – but no longer as a strategic military position, but a place of hope and beliefs.