Just which parties coalesce from among the three main blocs - the centre-right coalition, centre-left coalition and the anti-establishment 5-Star Movement - will determine Italy's course. The vote is being held under a complex new electoral law which means the final result might not be clear until late Monday.
If no party wins an overall majority, one scenario outlined by analysts could be a grand coalition between the PD and Forza Italia - a prospect that would reassure investors but risks spreading more cynicism and emboldening populists and the far-right.
The last opinion polls before the vote put Berlusconi's coalition in the lead with 37%, followed by the M5S with 28% and the centre-left with 27%.
Some pollsters say the League could overtake Berlsuconi's Forza Italia party on Sunday. "Salvini is the ideal man for Italy. the priority is to control the borders and then give a helping hand to the economy", Claudio Gaiola, an electronics goods maker from Turin who sported a baseball cap saying "Salvini premier", told Reuters.
Democratic Party leader Matteo Renzi told a final campaign event in his native Florence on Friday that only a vote for his party would prevent Salvini from taking power. The 5-Star Movement, set up in 2009 by stand-up comedian Beppe Grillo, hoped to capitalise on such disgust, particularly among Italy's young.
Antonio Tajani, president of the European Parliament, is a longtime ally of former prime minister Silvio Berlusconi.
President Sergio Mattarella can not 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.
Five Star leader Luigi Di Maio, 31, has vowed not to seek a coalition deal but appealed to rivals to back him if his party wins the most votes.
Prolonged political chaos would also have negative consequences for the EU.
Struggling Maplin and Toys R Us collapse into administration
Performance was also said to have been dented by soaring inflation, falling consumer spending and competition from online rivals. The stores will stay open for the moment but the online service and click-and-collect will be closed immediately.
Roberto D'Alimonte of Rome's LUISS University said such an alliance would be "catastrophic" for the financial markets.
"This election campaign has been pretty squalid, including from the Democratic Party (PD), who I voted for", 24-year-old barber Mirko Canali told AFP after casting his vote in Rome.
The 81-year-old politician is calling for major tax cuts and tighter immigration controls.
The billionaire tycoon can not himself hold office because of a tax fraud conviction but has put forward European Parliament President Antonio Tajani as his prime ministerial nominee.
Mr Tajani's moderate profile is aimed at allaying fears in Europe about his populist allies, notably the League, whose leader Matteo Salvini has promised to deport the 600,000 boat migrants who have arrived in Italy over the past four years. Describing himself as a "proud Catholic", he said Pope Francis had nevertheless "exacerbated the migrant crisis" with his call for Europe to open its arms to refugees.
Italy's interior ministry says the turnout for Italy's general election at noon (1100GMT) stands at 19.3 percent, five hours after polls opened.
In another gaffe, the cameras were watching as he made German Chancellor Angela Merkel wait for him to finish a phone call at a North Atlantic Treaty Organisation summit.
But mainstream parties in Italy have found it especially hard to contain voter anger, with the economy still 6 per cent smaller than a decade ago and unemployment stuck at about 11 per cent.
Another possibility could be a temporary government and eventually new elections.