Iran’s supreme leader certified the country’s election results on Tuesday, endorsing President-elect Ebrahim Raisi.
Ayatollah Ali Khamenei issued the decree during a ceremony attended by high-ranking Iranian officials.
Ultraconservative Mr Raisi is to be inaugurated on Thursday as the new president of Iran.
He will face tough challenges, including internal economic and health crises and navigating tension with the West.
"We will seek to lift the tyrannical sanctions imposed by America," Mr Raisi said in a televised speech after the ceremony.
He said his government would try to improve living conditions for those that have suffered under the sanctions.
Mr Raisi, 60, replaces moderate president Hassan Rouhani, whose landmark achievement was the 2015 nuclear deal between Iran and six world powers.
From the outset, Mr Raisi will have to tackle the nuclear talks, aimed at reviving the deal from which the US unilaterally withdrew.
He must also respond to US, Britain and Israel's warnings over a deadly tanker attack last week, for which Tehran denies responsibility.
Mr Raisi won a presidential poll in June in which more than half the electorate stayed away. Many political heavyweights were barred from standing.
A former judiciary chief, Mr Raisi has been criticised by the West for his human rights record.
The inauguration ceremony is to be held at 10.30am, local time, at the supreme leader's offices in central Tehran, state media said.
Traffic limitations are planned on streets around the venue with domestic air travel to and from the capital banned for two hours until noon, local media reported.
On Thursday, Mr Raisi will be sworn in before Parliament, where he is to submit his proposed government list.
His presidency will consolidate power in the hands of conservatives following their 2020 legislative election victory, marked by the disqualification of thousands of reformist or moderate candidates.
On July 27, Mr Raisi called on Parliament to co-operate to increase Iranians' hope in the future.
“I am very hopeful for the country's future and confident that it is possible to overcome difficulties and limitations,” he said in a statement.