Doclea or Duklja (Serbian Cyrillic: Дукља) was a medieval state with hereditary lands roughly encompassing the territories of present-day southeastern Montenegro, from Kotor on the west to the river Bojana on the east and to the sources of Zeta and Morača rivers on the north. Duklja was at first a vassal of the Eastern Roman Empire until it became a part of the Serbian Principality in the 9th century, under the Vlastimirović dynasty. After the Byzantine annexation of Serbia in the late 10th century, Duklja remained under Byzantine rule until the 1040s, when the local lord Stefan Vojislav managed to achieve independence for most of the maritime region under his rule; Duklja emerged as the most powerful polity, and became the center of the Serbian realm throughout the 11th century, ruled by the Vojislavljević dynasty.
In 1060, the Vojislavljevićs annexed "Rascia" (the hinterlands). With the death of Constantine Bodin, in 1101, a cadet branch of the dynasty succeeded in ruling Rascia independently, and in 1148 Duklja was incorporated in the latter - as a crown land of the Grand Principality of Serbia, subsequently referred to as Zeta, remaining so until the fall of the Serbian Empire. During the fall of the Serbian Empire, Zeta became semi-independent in 1362 under the Balšić family, until being reincorporated to the Serbian Despotate, and then finally conquered by the Ottoman Empire.