A right-wing alliance led by Giorgia Meloni's Brothers of Italy party is on course for a clear majority in the next parliament, giving the country its most right-wing government since World War II.
Meloni, as leader of the largest coalition party, is also likely to become Italy's first woman prime minister.
Meloni, 45, has pledged to support Western policy on Ukraine and not take undue risks with the third largest economy in the euro zone.
An exit poll by state broadcaster RAI said the bloc of conservative parties, that also includes Matteo Salvini's League and Silvio Berlusconi's Forza Italia party, won 41 to 45 percent of votes, enough to guarantee control of both houses of parliament.
"Centre-right clearly ahead both in the lower house and the Senate! It'll be a long night but even now I want to say thanks," Salvini said on Twitter.
Italy's electoral law favors groups that manage to create pre-ballot pacts, giving them an outsized number of seats by comparison with their vote tally.
RAI said the right-wing alliance would win 227 to 257 seats in the 400-strong lower house as well as 111 to 131 of the 200 Senate seats.
Full results are expected by early Monday.
The result caps a remarkable rise for Meloni, whose party won only 4 percent of the vote in the last national election in 2018, but this time around was forecast to emerge as Italy's largest group with 22 to 26 percent.
But it was not a ringing endorsement, with provisional data pointing to turnout of just 64.1 percent against 74 percent four years ago – a record low number in a country that has historically enjoyed a high level of voter participation.
Meloni didn't make any immediate comment after the exit poll was announced on RAI. But earlier, she tweeted to Italian voters: "Today you can help write history."
Italy has a history of political instability and the next prime minister will lead the country's 68th government since 1946 and face a host of problems, notably soaring energy costs and growing economic headwinds.
Italy has had three coalition governments since the last election. The election on Sunday was being held six months early after Premier Mario Draghi's pandemic unity government, which enjoyed wide citizen popularity, collapsed in late July.
Draghi remains as caretaker until a new government is sworn in.