Who are the key players in Italy's election?

Five men and one woman have emerged as the key players in one of the messiest election campaigns Italy has experienced in its 70-plus years as a republic.

From left: Silvio Berlusconi, Matteo Renzi, Luigi Di Maio, Matteo Salvini, Emma Bonino and Paolo Gentiloni. Source: AAP

What you need to know about the five men and one woman in the Italian election:

Silvio Berlusconi

At 81, Italy's three-time former premier is back in the political limelight, having survived the so-called bunga bunga sex scandal, a tax fraud conviction and open-heart surgery, recasting himself as a pro-EU statesman at the helm of a poll-leading rightist coalition.

Italian former prime minister and leader of 'Forza Italia' party Silvio Berlusconi. Source: AAP

However, Berlusconi's criminal record bars him from public office, and he has shown signs of physical fatigue while campaigning. His leadership is openly challenged by his hard-right ally Matteo Salvini, who covets the post of prime minister.

Matteo Renzi

The 43-year-old leader of the ruling centre-left Democratic Party (PD) is struggling to regain political momentum, still smarting from the constitutional referendum defeat of December 2016 that led to his resignation as prime minister.

Secretary of 'Partito Democratico' (Democratic Party) and former Prime Minister Matteo Renzi. Source: AAP

Formerly known as a "demolition man" who promised radical change, Renzi is now offering stability and "step-by-step" reforms.

But despite an improving economy and abating migration crisis, voters don't appear to be buying his message.

Luigi Di Maio

A 31-year-old former football stadium steward and waiter who has been serving as deputy speaker of the lower house of parliament, Di Maio has replaced comedian Beppe Grillo as leader of the anti-establishment Five Star Movement (M5S).

Luigi Di Maio from Five-Star Movement (M5S). Source: AAP

Under his leadership, the M5S has softened its image, dropping plans to hold a eurozone exit referendum. Pointing to the PD's slumping poll numbers, M5S is portraying itself to voters as the only alternative to Berlusconi's return.

Matteo Salvini

A firebrand populist who counts Vladimir Putin, Donald Trump and Marine Le Pen among his political heroes, the 44-year-old has revitalised his League party by campaigning against immigration and promising to put "Italians first."

The North League (LN) party's Matteo Salvini. Source: AAP

If the conservative bloc that includes Salvini wins the elections, and if the League wins more votes than Berlusconi's Forza Italia party, Salvini says he should become prime minister. Berlusconi is instead proposing EU parliament chief Antonio Tajani for the job.

Emma Bonino

A veteran civil rights campaigner who helped legalise abortion and divorce in the 1970s, the 69-year-old lung cancer survivor has managed to defy the prevailing mood in the country with an unashamedly pro-immigration and pro-EU message.

Emma Bonino, leader of the ' +Europa ' (More Europe) party. Source: AAP

Her "More Europe" party, allied with the PD, is expected to do well with liberal, metropolitan voters.

If it clears a 3 per cent barrier to enter parliament, it could have a pivotal role in a grand coalition scenario.

Paolo Gentiloni

The sitting prime minister, 63, is a PD stalwart with a dull public image, but a relatively solid record in government and a quiet and unassuming style that, in contrast to Renzi, has earned him high popularity ratings and few enemies.

Italian Premier Paolo Gentiloni. Source: ANSA

Along with Tajani, he is seen as an ideal candidate to lead a grand coalition government. In any case, if polls deliver a hung parliament, he will keep his job until the post-election deadlock is solved - which could take a while.