Over 50 million citizens, including some 4.7 million living abroad, are eligible to cast their ballots at 61,566 polling stations, which will remain open from 7 a.m. (0500 GMT) to 11 p.m. (2100 GMT) local time, Xinhua news agency reported.
They are set to choose the 400 deputies and 200 senators that will form the two houses of the next assembly.
A right-wing coalition and a center-left alliance are seen as the main contenders. Adding to them are a smaller coalition of two centrist parties, and the populist Five Star Movement (M5S), with both the coalition and the M5S running alone.
The right-wing alliance — made up of the nationalist Brothers of Italy, the League, and center-right Forza Italia — appeared to be leading in all opinion polls published up to two weeks before the vote.
Brothers of Italy appeared as the frontrunner, followed at a short distance by the Democratic Party, the key force of the center-left coalition.
Giorgia Meloni, leader of the Brothers of Italy, is therefore seen as a potential candidate for the post of next prime minister of Italy. If so, she would be the first woman to serve in such a role in the country.
For the first time ever, as a result of a recent constitutional reform, 18-year-olds in the country will be allowed to vote to elect the Senate and the Chamber of Deputies. This applies to almost 2.7 million young citizens who have just come of age, the Interior Ministry said.
Vote counting will begin soon after the closure of all polling stations, and early results are expected as soon as in the first hours of Monday.