Iran's electoral council has approved four candidates to run in the country's presidential elections on Friday. The BBC News website profiles the incumbent President Mahmoud Ahmadinejad, running for a second four-year term in office, and the three other candidates.
Ultra-conservative Mahmoud Ahmadinejad was far from the predictable winner of the 2005 presidential election.
Mr Ahmadinejad has developed a reputation for his fiery rhetoric
But the then-mayor of Tehran won the second round of the much-criticised poll, becoming the first non-cleric to hold the post.
The softly spoken son of a blacksmith ran on a platform of fighting poverty and corruption, and of sharing out the country's oil wealth. He presented himself as a humble man of the people, appealing directly to Iran's poor.
In the following years, he has developed a reputation internationally for his fiery rhetoric and verbal attacks on the US and Israel.
He has frustrated the West but pleased many in Iran by his refusal to give in to international demands to curtail his country's nuclear and missile development programme, maintaining his view that Iran has a right to civilian nuclear energy and denying the country is pursuing nuclear weapons.
In a speech at the UN in April 2009, his comments that Israel was a state founded on racist principles prompted a walk-out by delegates from at least 30 countries but earned him a hero's welcome on his return home.
Domestically, the president has been criticised for what some see as his antagonising of the US, and for his failure to tackle the country's economic problems.
Despite domestic criticism, he still has the support of the military, the Revolutionary Guards and the state-owned media which, analysts say, could make him a difficult candidate to unseat.
MIR HOSSEIN MOUSAVI
Former Iranian Prime Minister Mir Hossein Mousavi is widely regarded as the main challenger to incumbent President Mahmoud Ahmadinejad.
Mr Mousavi has vowed to improve relations with the West
A self-described "reformist who refers to the principles" of the 1979 Islamic revolution, he has vowed to combat Iran's "extremist" image abroad.
As prime minister from 1981 to 1989, when the post was abolished, he was praised for his deft handling of the Iranian economy during the bitter eight-year war with Iraq.
An architect and painter, Mr Mousavi has spent the past 20 years behind the scenes in Iranian politics, serving as a presidential adviser from 1989 to 2005 and on the Expediency Council, Iran's top arbitration body.
He has secured the backing of Mohammad Khatami, Iran's former reformist president, in his bid for a political comeback.
Now 68, Mr Mousavi has called for greater personal freedoms in Iran and criticised the ban on private television channels.
But he has refused to back down from the country's disputed nuclear programme, saying it is for peaceful purposes.
Mr Mousavi, who speaks Farsi, English and Arabic, is currently the president of the Iranian Academy of Arts.
A former head of Iran's powerful Revolutionary Guards, Mohsen Rezai was the first of Iran's four main contenders to register his candidacy for the presidential race.
Mr Rezai led the Revolutionary Guards during the eight-year war with Iraq
The 54-year-old is the only conservative challenger to incumbent President Mahmoud Ahmadinejad.
Mr Rezai also ran in the 2005 election, but pulled out just ahead of voting day.
A self-proclaimed critic of Mr Ahmadinejad, he has accused the Iranian leader of pushing the country to the edge of a "precipice" and promised to reform Iran's struggling economy.
A veteran military man who also holds a PhD in economics, Mr Rezai is now vowing to fight poverty, inflation and unemployment.
On the issue of Iran's disputed nuclear programme, he has accused Mr Ahmadinejad of using "adventurous language", and vowed to "neither support passivity nor adventurism".
His impressive military record started before the 1979 Islamic revolution as a member of an armed militia that opposed the US-backed Shah.
He was appointed as the commander of the Revolutionary Guards Corps at the age of 27, and led the force during the bloody eight-year war with Iraq.
Mr Rezai went on to become the secretary of Iran's Expediency Council - the country's top arbitration body - in 1997.
He is one of five Iranian officials wanted in Argentina for their alleged involvement in an attack on a Jewish centre that killed 85 people in 1994.
Reformist Mehdi Karroubi, 72, was speaker of parliament from 1989 to 1992, at a time when the Iranian parliament was dominated by Islamic radicals.
Mr Karroubi criticised the elections which elected Mr Ahmadinejad
He was praised by many MPs in 2002, when he led a walk out in protest at the jailing of a fellow reformist politician.
He came a close third in the 2005 elections, but criticised the process, saying there had been "bizarre interference" in the polls and that money had changed hands to influence the results.
Mr Karroubi, the only candidate to refer to himself as reformist, has openly opposed many of Mr Ahmadinejad's policies and is one of the few politicians to have criticised the president's dismissal of the Holocaust.
He has promised that if elected he would adopt a "policy of detente" with other countries, a step away from Mr Ahmadinejad's more provocative approach.
He told the AFP news agency he would "adopt the middle path" in Iran, to bring in social, economic and political reforms without alienating hard liners.
Mr Karroubi has insisted that the Revolutionary Guard must not interfere in the June poll, and that his defeat or victory must be "according to the people's mandate".