Results are expected around noon Saturday.
"Everything that the Iranian people do today until tonight, by going to the polls and voting, serves to build their future".
As night fell Friday, turnout appeared far lower than in Iran's last presidential election in 2017.
Social media posts from inside Iran also indicated that voting was light at polling stations around the country. More than 59 million Iranians are eligible to vote. Among them were Supreme Leader Ayatollah Ali Khamenei, outgoing President Hassan Rouhani, who is ending an eight-year term, and leading presidential candidate Raisi, a Khamenei protege whom many Iranians expect to easily win the race.
Iranian opposition groups overseas and some dissidents at home have urged a boycott of the vote they see as an engineered victory for Mr. Raisi, the 60-year-old head of the judiciary, to cement ultraconservative control. "That is why the ruling system has always put emphasis on voter participation and used all possible means to bring people to the polls".
With economic misery palpable at home, Iran's rulers can not risk starting the talks from scratch after the election, as the ruling clerics are aware their political fortunes rely on tackling worsening economic hardship.
Three of the seven approved presidential candidates withdrew from the contest on Wednesday, two of them ultraconservatives like Raisi and one a relative moderate.
The only reformist still running is low-profile former central bank chief Abdolnaser Hemmati, who has promised to revive the economy and, unusually in Iran, heavily involved his wife in campaigning.
The victor will take over in August as Iran's eighth president from incumbent Hassan Rouhani, a moderate who has served the maximum of two consecutive four-year-terms allowed under the constitution.
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Opinion polling by state-linked organizations, along with analysts, indicated that Raisi - who is under USA sanctions for his role in mass executions - was the front-runner in a field of only four candidates.
Out of an initial field of nearly 600 hopefuls for the presidency, only seven - all men - were approved to run by the Guardian Council, a body of 12 clerics and jurists.
Regardless of who wins, Khamenei remains Iran's ultimate decision-maker in matters of foreign and nuclear policy.
It also would firmly put hardliners in control across the Iranian government as negotiations in Vienna continue over trying to save Tehran's tattered nuclear deal with world powers as it enriches uranium to the closest point yet to weapons-grade levels.
President Joe Biden's administration has said it could ease the sanctions if Iran agreed to resume curbs on nuclear activities that could be weaponized.
Over 50 per cent of Iran's 85 million population has been pushed under the poverty line since 2018, when then US President Donald Trump ditched a 2015 nuclear deal and reimposed nuclear-related sanctions that have squeezed Tehran's oil income.
Trump said the JCPOA did not do enough to prevent Iran from developing nuclear weapons - a goal it denies having - or engaging in other objectionable activities.
"For the first time since the foundation of the Islamic republic, the election of the president will take place without any real competition", wrote former French ambassador Michel Duclos in a commentary for Paris think-tank the Institut Montaigne. Khamenei served as Iranian president himself before being appointed supreme leader in 1989.
"If Khamenei deems Raisi a success, I think he will propose Raisi to succeed him".