Although National Rally is expected to win the most seats in the National Assembly, the latest opinion polls indicated it might fall short of an absolute majority.
A hung parliament would severely dent President Emmanuel Macron's authority and herald a prolonged period of instability and policy deadlock in the euro zone's second-biggest economy.
French polls suggest National Rally's Marine Le Pen and Jordan Bardella won't reach a majority. (AP PHOTO)
Should the nationalist, Eurosceptic National Rally secure a majority, it would usher in France's first far-right government since World War II and send shockwaves through the European Union at a time when populist parties are strengthening support across the continent.
Turnout stood at 26.3 per cent by midday (1000 GMT) on Sunday, up from 18.99 per cent during the second voting round in 2022, the interior ministry said, highlighting the population's extreme interest in an election that has highlighted polarised views in France.
It was the highest midday turnout level since 1981, pollsters Harris Interactive and Ipsos said.
Voting closes at 6pm. (1600 GMT) in towns and small cities and 8pm in bigger cities.
Pollsters will deliver initial projections based on early counts from a sample of voting stations when city booths close.
Opinion polls forecast Marine Le Pen's National Rally will emerge as the dominant force in the National Assembly as voters punish Macron over a cost of living crisis and being out of touch with the hardships people face.
However, National Rally is seen failing to reach the 289-seat target that would outright hand Le Pen's 28-year-old protege Jordan Bardella the prime minister's job with a working majority.
France's snap election could produce a hung parliament and years of political deadlock. (AP PHOTO)
The far right's projected margin of victory has narrowed since Macron's centrist Together alliance and the left-wing New Popular Front pulled scores of candidates from three-way races in the second round in a bid to unify the anti-National Rally vote.
"France is on the cliff-edge and we don't know if we're going to jump," Raphael Glucksmann, a member of the European Parliament who led France's leftist ticket in June's European vote, told France Inter radio.
Political violence surged during the short three-week campaign.
Interior Minister Gerald Darmanin has said authorities recorded more than 50 physical assaults on candidates and campaigners.
Some luxury boutiques along the Champs Elysees boulevard, including the Louis Vuitton store, barricaded windows and Darmanin said he was deploying 30,000 police amid concerns of violent protests should the far-right win.
A longtime pariah for many due to its history of racism and anti-Semitism, National Rally has broadened its support beyond its traditional base along the Mediterranean coast and the de-industrialised north, tapping into voter anger at Macron over straitened household budgets, security, and immigration worries.
"French people have a real desire for change," Le Pen told TF1 TV on Wednesday.
France's parliamentary election could produce its first far-right government since World War II. (AP PHOTO)
Macron stunned the country and angered many of his political allies and supporters when he called the snap election after a humbling by National Rally in the European parliamentary vote, hoping to wrong-foot his rivals in a legislative election.
Whatever the final result, his political agenda now appears dead, three years before the end of his presidency.
A National Rally-led government would raise major questions over who speaks for France in Europe and on the global stage, and over where the EU is headed given France's powerful role in the bloc.
EU laws would be almost certain to restrict its plans to crack down on immigration.
National Rally pledges to reduce immigration, loosen legislation to expel illegal migrants and tighten rules around family reunification.
On the economy, National Rally has watered down some of its frontline policy pledges to shore up household spending and lower the retirement age, constrained by France's ballooning budget deficit.
Bardella has said National Rally would decline to form a government if it did not win a majority, although Le Pen has not ruled it out.
