Here are brief descriptions of each of the six men who were approved by the Guardians Council to run in Iran's upcoming presidential vote. A first round is scheduled for May 19, with a possible second-round runoff if no candidate gets more than half of the vote.
Update: Two of the candidates, Mohammad Bagher Ghalibaf and Eshagh Jahangiri have dropped out of the race, as of mid-day May 17. There can be other withdrawals before the deadline on mid-night, May 17.
President Hassan Rohani
A relatively moderate cleric, Rohani, 68, came to power in 2013 by promising to improve ties with the West, give Iranians more rights, and lessen state intervention in their lives.
A former nuclear negotiator, Rohani oversaw the landmark nuclear deal in 2015 that ended a decade-old standoff with the West. Under the deal, Iran significantly limited its sensitive nuclear activities in exchange for sanctions relief.
Iranian President Hassan Rohani gestures to the camera after registering to run for reelection at the Interior Ministry in Tehran on April 14.
During a 2013 trip to New York to attend the UN General Summit, Rohani shared an unprecedented phone call with former U.S. President Barack Obama. The call, the first between the presidents of the two countries since 1979, was criticized by hard-liners in Iran.
Rohani's critics say he has given too much away and the deal has failed to revive Iran's economy or improve the lives of the country's poor.
Rohani, who has a doctorate of law from the Glasgow Caledonian University, is supported primarily by reformists and so-called pragmatists, but also by some conservatives.
Ebrahim Raisi
Raisi is a cleric and former prosecutor who is seen as being close to Supreme Leader Ayatollah Ali Khamenei. As such, he could present the strongest challenge to Rohani's reelection.
Raisi, 56, was appointed last year to the prestigious chairmanship of Iran's wealthiest state charity.
He is presenting himself as a candidate of the poor while promising to create jobs and fight corruption. Raisi recently told state controlled TV that he has personally tasted "poverty and deprivation" in his life.
He served in senior posts in the hard-line judiciary, a major tool of state repression in Iran. Raisi was reportedly involved in the mass executions of opponents and political prisoners in the 1980s.
There's been speculation that Raisi could succeed Khamenei, who served two terms as president before becoming supreme leader -- the position in Iran's clerically dominated system that has the last say in political, religious, and military matters.
If major elements within Iran's conservative leadership are keen on Raisi eventually becoming supreme leader, that could significantly raise the stakes on his presidential bid.
Mohammad Baqer Qalibaf
Tehran's mayor, Qalibaf has already run twice unsuccessfully for president. Once was in 2005, when he was defeated by hard-liner (and mayoral predecessor) Mahmud Ahmadinejad. The second time, in 2013, he finished a distant second behind Rohani.
Qalibaf, 56, has criticized Rohani's economic policies and pledged to create jobs.
A former police chief and air-force commander within the Islamic Revolutionary Guards Corps (IRGC), Qalibaf has publicly boasted of his active role in suppressing student protests in 1999 and 2003, and after the much-criticized presidential election in 2009.
Qalibaf was among some two dozen IRGC commanders who penned a letter to then-President Mohammad Khatami threatening the reform-minded leader with intervention if he didn't rein in the 1999 student protests.
He was criticized and accused of incompetence after the deadly collapse of an iconic building in the Iranian capital in January. Some people called for his resignation as mayor. His supporters said the attacks against him were politically motivated.
Qalibaf has also been accused of corruption over reports that he allowed the sale of discounted land in Tehran to politicians.
Eshaq Jahangiri
Iran's first vice president, Jahangiri is widely seen as having registered for the election to stand by Rohani in the face of attacks by rivals and to defend the government's policies, particularly during the planned debates.
Jahangiri served as minister of industries and mines in 1997-2005, under reformist President Khatami.
He reportedly worked with the 2009 presidential campaign of ex-Prime Minister Mir Hossein Musavi, an opposition leader who has been under house arrest since 2011.
Jahangiri is said to have good ties with Supreme Leader Khamenei and his closest allies.
Mostafa Mirsalim
Mirsalim is a former culture minister whose 1994-97 tenure was marked with increased restrictions and censorship.
He has criticized Rohani's outreach to the West as ineffectual, saying the result has been new restrictions on Iran and continued sanctions against the country.
The French-educated Mirsalim teaches mechanical engineering at Tehran's Amir Kabir University. He served as police chief following the 1979 revolution.
Mostafa Hashemitaba
Hashemitaba is a former head of the Iranian National Olympic Committee who is widely seen as a centrist.
He has vowed to improve the quality of life for Iranians and fight corruption.
At 71, Hashemitaba is the oldest candidate in the race.
He ran for president in 2001 and finished 10th, winning a paltry 28,000 votes.