Some 18,000 kilometres (11,000 miles) from the French mainland, New Caledonia is home to a quarter of the world's known supplies of nickel -- a vital electronics component -- and is a strategic foothold for France in the Pacific.
Voting in the archipelago's 284 polling stations ended at 6 pm local time (6 am GMT), with results expected Sunday evening.
One hour before polling stations closed, officials put voter turnout at just over 73 percent.
Some 175,000 people were eligible to vote in the remote islands fringed by spectacular beaches, with opinion polls predicting a large majority in favour of staying French.
But there were fears the referendum could inflame tensions between indigenous Kanak people, who tend to favour independence, and the white population, which boiled over into deadly violence in the 1980s.
The quasi-civil war claimed more than 70 lives. It led to the 1998 Noumea Accord which paved the way for the steady devolution of powers as well as Sunday's referendum.
On Friday, separatist activists drove along Noumea's waterfront in a convoy of around 20 cars, waving the Kanak flag to cries of "Kanaky" -- their name for New Caledonia.
Separatists have urged Kanak voters to choose self-determination, throwing off the shackles of "colonial" authorities in Paris.
But indigenous people make up less than 50 percent of the electorate and some Kanaks back staying part of France, not least due to the 1.3 billion euros the French state hands to the islands every year.
Going it alone
"I'm not sure we have all the assets we'd need to succeed," said Marc Gnipate, a 62-year-old pensioner.
Under the 1998 deal, in the event of a "no" vote two further referendums on independence can still be held before 2022.
French President Emmanuel Macron is set to give a televised address shortly after the results are announced on Sunday.
He has largely stayed clear of the campaign, but declared during a visit to Noumea in May that "France would be less beautiful without New Caledonia".
Macron also raised concerns over increasing Chinese influence in the Pacific, where Beijing has invested heavily in Vanuatu, a territory which broke from France and Britain in 1980.
Accusing the US of "turning its back on the region in recent months", Macron said China was "building its hegemony step by step" in the Pacific -- suggesting an independent New Caledonia could provide Beijing's next foothold.
A previous referendum in 1987 was undermined after Kanak's boycotted the vote claiming the terms of voter eligibility were unfair. This time round only residents of 20 years or longer can vote, excluding many white European migrants with a weak connection to the territory.
Australia has also expressed concerns about China's activities in neighbouring island states -- which the Lowy Institute think-tank estimates received $1.78 billion in aid from Beijing from 2006-16 -- boosting its own spending in response.
While Australia officially remains neutral on New Caledonia's independence vote, Canberra's former consul-general in Noumea Denise Fisher said it appreciated the stability France's Pacific presence offered in the face of China's rise.
"It's been fortunate for Australia to have a well-resourced Western ally such as France engaged in the region, particularly at a time when there's a lot of geo-strategic change and new players like China coming into the region," she told the ABC.
"There are a few uncertainties arising now."
Home to 269,000 people, New Caledonia is one of a handful of French island outposts -- a legacy of the country's 19th-century empire -- which retain strategic importance.
The referendum will be a test of the appeal of remaining part of France for such far-flung territories, which are heavily dependent on state handouts but where many feel overlooked by Paris.
Both French Guiana in South America and the Indian Ocean archipelago of Mayotte have been rocked since last year by major protests over living standards and perceived neglect.
In New Caledonia, there are fears that the vote could expose tensions over stark inequalities which persist despite government efforts to redress the economic balance in favour of Kanaks.
"In Noumea people earn a salary, but in the tribes no one earns a salary or any kind of monetary income," said veteran Kanak activist Elie Poigoune.
The Kanak community is plagued by high school dropout rates, chronic unemployment and poor housing conditions.
Gangs of delinquent youths have become increasingly common on the streets and both sides fear violence among them if the "no" vote prevails.