Heavily indebted Italy is the third largest economy in the 19-member euro zone – but the ailing economy along with concerns over mass immigration and unemployment have thrown the government into chaos.
The vote could bring political gridlock to Italy as no bloc is predicted to win enough votes to form a majority in government.
Since the fall of fascism, all electoral laws have been re-written, so no single party can run by itself, instead seats are distributed in a proportional way.
Polling stations for the italian election 2018 close at 11pm (10pm GMT), with exit polls due immediately afterwards.
Who will win the Italian election today?
Pollsters predict former prime minister Silvio Berlusconi and his right-wing allies La Lega and Brothers of Italy will emerge as the largest bloc in parliament, but fall short of a parliamentary majority.
The anti-establishment Five Star Movement looks set to be the biggest single party, feeding off discontent over entrenched corruption and growing poverty.
While the ruling centre-left Democratic Party (PD) is expected to limp home in third place.
“There was momentum for 5-Star in the final days of the campaign, but it is hard to see any party or coalition getting the 40 percent needed to form a government,” said Lorenzo Pregliasco, co-founder of YouTrend pollsters.
Some pollsters say La Lega could overtake Berlsuconi’s Forza Italia party on Sunday.
Populist parties have been on the rise across Europe since the 2008 financial crisis, but mainstream parties in Italy have found it especially hard to contain voter anger, with the economy still some six percent smaller than a decade ago and unemployment stuck at around 11 percent.
M5S, led by 31-year-old Luigi Di Maio, has been particularly successful at tapping into the disaffection in the underdeveloped south, and even promised a monthly universal wage of up to 780 euros ($960) for the poor.
“There is a sense of anger and a lack of trust amongst part of the electorate. We need to see if that leads to abstention or a protest vote for 5-Star or the League,” said Pregliasco.
Although all party leaders have ruled out any post-election alliances with rivals, Italy has a long history of finding a way out of apparently intractable political stalemate.
According to Paolo Cossarini, teaching fellow in Politics and International Relations at Loughborough University, he has predicted the vote percentage of the main blocs as follows:
Bloc 1: Centre right bloc (FI, FdI, LN): 34-37%
Bloc 2: Centre Left (PD, + others): 30%
Party not in pre-electoral alliance – 5 Star Movement: 25-28%
But if, as expected, no-one clinches a clearcut victory on Sunday, it might take weeks before a government deal is reached.
President Sergio Mattarella cannot launch any formal coalition talks until after the new parliament has sat on March 23 and the next prime minister will need to win votes of confidence in both houses before taking office.