Doclea or Duklja is 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 is at first a vassal of the Eastern Roman Empire until it becomes 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 remains under Byzantine rule until the 1040s, when the local lord Stefan Vojislav manages to achieve independence for most of the maritime region under his rule; Duklja emerges as the most powerful polity, ruled by the Vojislavljević dynasty.In 1060, the Vojislavljevićs annex "Rascia" (the hinterlands which will later be the nucleus of Serbia) and installs vassal rulers there.

With the death of Constantine Bodin, in 1101, a cadet branch of the dynasty succeeds in ruling Rascia independently, and in 1189 Duklja is 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 becomes independent in 1356 under the Balšić family, and again reincorporated to the Serbian Despotate from 1421 to 1427.