Israelis are voting in a third general election in less than a year, with the prime minister fighting for his political survival.
Neither Benjamin Netanyahu nor his main challenger, Benny Gantz, were able to put together majority coalitions following the last two elections.
The final opinion polls suggested the latest round is too close to call.
Mr Netanyahu is seeking re-election two weeks before he is due to stand trial on corruption charges.
He has been ordered to appear in court in Jerusalem on 17 March to hear the indictment against him.
The prime minister was charged in November with bribery, fraud and breach of trust in connection with three separate cases. He has strongly denied any wrongdoing, saying he is the victim of a politically motivated “witch hunt”.
Opponents have called on Mr Netanyahu to step down. But even if convicted, he would not be required to do so until the appeals process was exhausted.
Mr Netanyahu, 70, is Israel’s longest-serving prime minister, having been in office from 1996 to 1999 and again from 2009. In December, he comfortably won a primary election for leadership of his right-wing Likud party.
His main opponent in the general election is Benny Gantz, 60, a retired general who served as chief of staff of the Israel Defense Forces (IDF) before entering politics to lead the centrist Blue and White party.
Israel’s political system is based on a form of proportional representation, with parties winning seats based on the number of votes they receive rather than which party gets the most in a particular constituency. This means governments have always been coalitions, sometimes fractious and short-lived.
Mr Netanyahu’s previous coalition lasted for four years before an early election was held in April 2019.
Despite complaints among voters of election fatigue, Monday’s could be one of the most important for years.
If Blue and White wins, it will bring to an end more than 10 years of rule by Likud, which advocates a right-wing nationalist agenda.
If Likud wins and can form a governing coalition, Mr Netanyahu has vowed to annex Jewish settlements and a large corridor of land known as the Jordan Valley, both in the occupied West Bank.
Such a move was made more possible after US President Donald Trump released his Middle peace plan in January. Mr Trump said the US would “recognize Israeli sovereignty over the territory that my vision provides to be part of the State of Israel”, including parts of the West Bank – a departure from previous US positions.
The Trump plan has also been endorsed by Mr Gantz, and while he too has pledged to annex the Jordan Valley and the main settlement blocs, it is less clear whether he would go as far as Mr Netanyahu.
More than 600,000 Jews live in about 140 settlements built since Israel’s 1967 occupation of the West Bank and East Jerusalem. The settlements are considered illegal under international law, though Israel disputes this. The US has also declared it no longer sees the settlements as illegal.
The Palestinians – who have rejected Mr Trump’s peace plan as one-sided – insist that all the settlements must be removed if there is to be final peace deal.