On December 10, 1991, the Nagorno-Karabakh Republic declared independence from Azerbaijan, but despite having its own flag, military and government remains unrecognised as a separate state by other countries, including Armenia.
Nagorno-Karabakh's separatist government continues to seek recognition.
Azerbaijan wants to restore its control over the region.
Sporadic clashes inside the territory between Azeri and ethnic Armenian fighters began in 1988 and escalated to full-scale hostilities in 1992 between Azeri forces and troops from the neighbouring state of Armenia.
About 35,000 people have died in the conflict and up to one million people have been displaced.
A ceasefire was signed in 1994 but a peace deal has yet to be successfully brokered.
The Karabakh vote follows similar polls in a number of other unrecognised former Soviet Union states, including Georgia's breakaway South Ossetia and Moldova's Transdniestr earlier this year.