The Venezuelan government has called the referendum to measure popular support for its historical claim to a contested oil-rich swathe of jungle currently administered by Guyana.
The 159,500-sq-km (61,600-square-mile) region is known as Essequibo and makes up two thirds of the total of the land currently controlled by Guyana. It is home to 125,000 of Guyana's 800,000 citizens.
The dispute over the area has been rumbling on for more than a century.
In 1899, an international arbitral tribunal awarded the area to Britain, which at the time was the colonial power ruling over Guyana, or British Guiana, as it was then known.
But this ruling has been dismissed as unfair by successive Venezuelan governments over the past 60 years.
In 1966, Britain and Venezuela reached an agreement - known as the Geneva Agreement - to establish a commission made up of representatives of Guyana, which became independent from Britain that same year, and Venezuela to revisit the territorial dispute.
But even though almost six decades have passed since, there still has been no resolution.
The dispute flared up in 2015, after US giant ExxonMobil discovered oil in Essequibo's offshore waters.
In 2018, Guyana took the case to the International Court of Justice (ICJ), after being given the green light by the Secretary-General of the United Nations.
The ICJ, based in The Hague, in the Netherlands, is the principal judicial body of the United Nations, with one of its primary roles being the resolution of legal disputes between states.
It can take years for the ICJ to issue rulings and the first step in most cases is for it to decide whether it has jurisdiction, that is whether it has the legal authority to rule on a particular dispute.
In 2020, the ICJ ruled that it had jurisdiction to hear the dispute but it has yet to decide on the merits of the case, meaning whether the 1899 arbitral award giving the Essequibo to Guyana stands.
Venezuela has not accepted that the ICJ has jurisdiction but has so far continued to attend the court's hearings.
Tension rose further, when the government of Guyana held an auction in September of this year at which oil companies bid for exploration licences in Essequibo waters.
This move and a further "significant" new oil discovery made in those waters just over a month ago has increased the pressure on the Venezuelan government.
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