Italians voted on 25 September to return the country's most right-wing government since World War II, and allow Giorgia Meloni to become its first female prime minister.
A right-wing alliance led by Meloni's Brothers of Italy appeared poised for a clear victory when the last opinion polls were published two weeks ago.
There was still scope for a surprise with a polls blackout in force in the two weeks before the election.
The polls will be open at 7 am and the polls will continue until 11 pm when exit polls are published.
The complex calculations required by a hybrid proportional first-past electoral law mean it may be many hours before the composition of a new slimmed-down parliament is known.
Parts of Italy had heavy rainfall on Sunday, with the Campania region around the southern city of Naples particularly badly affected. With turnout only 51 per cent at the end of the day, it seemed to have put off some voters, with turnout only around 51 per cent at the same time in 2018, compared to more than 58 per cent at the same time in 2018.
Matteo Salvini, the leader of the League party, was one of Meloni's main allies as he voted in Milan on Sunday morning.
Meloni would be the obvious candidate for prime minister as the leader of an alliance that also includes former premier Silvio Berlusconi's Forza Italia.
Berlusconi, 85, voted in Milan, wearing one of his typical double-breasted suits. Meloni was expected to vote in her home city of Rome on Sunday evening.
A Rome resident said he was hoping that the right would win.
The left, from what I hear, has no serious manifesto, and the parties are on their own, while the right has a coalition, said the voter who gave his name as Paolo.
The next government is unlikely to take office before October, with the new parliament not meeting until October 13 if there is a clear cut.
The victory would cap a remarkable rise for Meloni, whose party won only 4 per cent of the vote in the last national election in 2018.
Meloni, 45, plays down her party's post-fascist roots and portrays it as a mainstream conservative group. She pledged to support Western policy on Ukraine and not take unnecessary risks with an economy hit hard by rising prices.
Italy's first autumn national election in more than a century was triggered by party infighting that brought down Prime Minister Mario Draghi's broad national unity government in July.
Italy has had a history of political instability and the next prime minister will lead the country's 68th government since 1946 and face a host of challenges, including rising energy costs.
The outcome of the vote will be watched nervously in European capitals and financial markets.
After Russia invaded Ukraine, European Union leaders are worried that Italy will be a more unpredictable partner than under Draghi, the former European Central Bank chief.
There are constant worries about Italy's ability to manage a debt pile that amounts to around 150 per cent of gross domestic product.