With the development of the science of geography in the Islamic world in the 9-10th century, Muslim geographers wrote important works providing information about the countries, regions and cities of that period, especially Islamic geography. The geography of Iran, which came under Arab-Islamic rule in the 7th century, occupies an important place in the works of Muslim geographers. The region of Djibāl, which extends from Mesopotamia in the west to the great Iranian desert in the east and is described by Muslim geographers as mountains because of its mountainousness, has been examined in detail in the works of the authors. This region was home to cities such as Rayy, Hamadan, Isfahan, Kermanshah, which had an important place in the ancient and medieval ages, as well as many smaller cities, but of great importance, compared to the aforementioned cities. In this study, the information about the region of Djibal has been compiled and evaluated based on the works of medieval Islamic geographers.