Eight candidates were approved to stand in the presidential elections by Iran's Guardian Council. Two of the candidates withdrew days before the poll. The winner will replace incumbent President Mahmoud Ahmadinejad, who is constitutionally barred form seeking re-election. Here are the candidates' profiles.
Iran's top nuclear negotiator, Saeed Jalili, is running for president for the first time. He is said to be very close to Supreme Leader Ayatollah Ali Khamenei.
He first came to prominence after he was appointed as the secretary of the Supreme National Security Council and Iran's top negotiator with the West in September 2007.
Born in the north-eastern city of Mashhad in 1965, he joined the paramilitary Basij force and served in the Iran-Iraq war (1980-88) on several tours of duty as a volunteer. He was wounded in combat and lost his right leg.
A PhD holder, Mr Jalili wrote his doctoral thesis on the "political thought in the Koran". Iranian news websites have portrayed him as an intellectual loyal to Islamic "ideals" and leading the "simple life".
His critics say he lacks the administrative experience to run the country, especially at a time when Iran is suffering from West-imposed sanctions over its nuclear programme.
The current mayor of Tehran, Mohammad Baqer Qalibaf is seen as a pragmatic conservative, loyal to the Supreme Leader.
The 51-year-old is a former military and police commander who later turned to politics, coming fourth in the 2005 presidential election.
The mayor has often been critical of President Mahmoud Ahmadinejad's policies, particularly regarding the economy and his management of the country; and was also closely associated with a coalition of conservative critics of the outgoing president.
Mr Qalibaf had previously served as head of the air force wing of Iran's elite Revolutionary Guards and is a frontline veteran of the 1980-88 Iran-Iraq war before becoming the national chief of police.
He is credited with firm tactics that suppressed student protests peacefully in 2003, and initiated popular police reforms in which women were allowed to serve for the first time.
A qualified pilot, Mr Qalibaf was reportedly still moonlighting for Iran Air and flying Airbus jets whilst holding his post as head of the country's police forces. He is also a lecturer at Tehran University.
Few candidates can match the political experience of Ali Akbar Velayati, the Supreme Leader's longstanding advisor on international affairs, who is also Iran's longest-serving minister since the 1979 revolution.
Seen as an irreproachable character, he is sometimes referred to by the public as "Mr may I", suggesting he seeks permission from the Supreme Leader at all times. He has been Ayatollah Khamenei's advisor since 1997, and is also the secretary-general of the World Assembly of Islamic Awakening.
Mr Velayati was born in 1945 in Tehran. A qualified medical doctor, he served as the deputy health minister from 1980 to 1981 and then as foreign minister for an unprecedented 16 years, from 1981 to 1997.
He belongs to the same "principle-ist" or conservative coalition as presidential candidates MP Haddad-Adel and Tehran Mayor Mohammad Baqer Qalibaf.
Hassan Rouhani is a key figure in Iranian politics, having held several parliamentary posts such as Deputy Speaker and Ayatollah Khamenei's representative at the Supreme National Security Council.
Mr Rouhani has been a chief negotiator in nuclear talks with the EU, and he currently heads the Expediency Council's Strategic Research Centre.
The 64-year-old cleric is often described as a "moderate" or "pragmatic conservative". He has openly criticised President Ahmadinejad by saying that his "careless, uncalculated and unstudied remarks" have cost the country dearly.
During student demonstrations against the closure of a reformist newspaper in 1999, Mr Rouhani adopted a tough stance, declaring that those arrested for sabotage and destroying state property would face the death penalty if found guilty.
But more recently, he supported the demonstrations that erupted after the 2009 election and criticised the government for opposing what he saw as the people's right to peacefully protest.
Mr Rouhani is said to be fluent in English, German, French, Russian, and Arabic, and has a law doctorate from Glasgow Caledonian University.
Gholamali Haddad-Adel withdrew from the race four days before the elections "to help promote the conservative victory". Mr Haddad-Adel is seen as completely loyal to the Supreme Leader, an impression reinforced by his family ties by marriage to the Khamenei family. Mr Haddad-Adel's daughter is the wife of Ayatollah Khamenei's son Mojtaba.
Although these connections were regarded by some as a strong point in the elections, he was seen to be lacking in oratory skills. In addition, some wonder why there seems to be little information available about his role in the 1979 Islamic Revolution. In Iran's political arena, being a revolutionary activist is an important advantage for political figures.
The 68-year-old MP for Tehran served as parliamentary Speaker from 2004-2008 and has been a parliamentarian since 2000. He has held several positions in the Islamic system since the revolution and he was the first non-cleric Speaker of parliament. He has also written several religious books, and is fluent in Arabic and English.
Mr Haddad-Adel was part of the same conservative coalition as Ali Akbar Velayati and Mohammad Baqer Qalibaf.
Mohammad Reza Aref pulled out of the race three days before the poll, saying the head of the reformist movement, former President Mohammad Khatami, had asked him to withdraw. A reformist politician, Mr Aref is also a member of the Expediency Council, a top advisory body to the Supreme Leader.
Born in 1951 in the central city of Yazd, Mr Aref has held various executive posts in post-revolutionary Iran. Seen as intelligent and well-educated, his reputation rests on his scientific achievements as much as his political record. Mr Aref studied electrical engineering at Stanford University, and currently teaches at Tehran's prestigious Sharif University of Technology.
Unlike many other reformist figures, he was not targeted by Iran's hardliners after the disputed 2009 elections. He has been a somewhat reluctant candidate in the past, having registered and subsequently withdrawn from two previous elections. Mr Aref had said that if Mr Khatami joined the 2013 election as a candidate, he would step aside.
Mr Aref's wife caused a stir in the media on the day of his registration, as she appeared by his side in more relaxed Islamic dress than other potential first ladies, rather than the traditional chador.
Mohsen Rezai currently holds the post of secretary of the influential expediency council headed by Akbar Hashemi Rafsanjani, with whom he seems to have a good working relationship.
A major-general who has served for over 15 years as the commander of the Islamic Revolution Guard Corps, Mr Rezai has been accused by Argentina of involvement in the 1994 attack on a Jewish centre in Buenos Aires which killed 85 people, and is on Interpol's Wanted List.
Mr Rezai registered as a presidential candidate in 2005 but then withdrew his candidacy, and in 2009 when he came in third place with only 1.7% of the vote. Mr Rezai initially contested the outcome along with the other candidates, alleging fraud, but later withdrew from protests after the Supreme Leader decided to back Mr Ahmadinejad's victory and refused to respond to the allegations.
He is regarded as a close ally of Supreme Leader Ali Khamenei and is seen as a conservative, but has been highly critical of Ahmadinejad's government, particularly on economic issues.
He was born in 1954 in Masjed-e-Soleyman and holds a doctorate in economics from Tehran University.
Mohammad Gharazi, a name little heard on Iran's political stage, is running for president for the first time. He is arguably the most low-key candidate in this election round, having been away from the country's political scene since 1997.
The Guardian Council's decision to approve Mr Gharazi to stand in the election took Iran's media by surprise. He was quoted as saying that he had neither a political party, nor any money to spend on a campaign.
He is best described as a moderate figure and is running under the campaign slogan of "government of no inflation".
Mr Gharazi was born in the central city of Isfahan in 1941 and studied engineering in Iran and France. He was politically active during the Shah's rule, as a result of which he was sent to prison in 1971 and later moved abroad.
He has had a varied political career in Iran since the 1980s, serving as oil minister, telecommunications minister and as governor of Iran's southern province of Khuzestan and western province of Kordestan.