Iran elects a new president Friday, with the ultraconservative cleric Ebrahim Raisi widely expected to take over from moderate Hassan Rouhani who has served two terms.
Here are landmark events in the history of the country, once known as Persia, since the 1979 revolution that overthrew the US-backed monarchy and established an Islamic republic.
- 1979 Islamic republic-
After months of protests, on January 16, 1979, the US-backed shah, Mohammad Reza Pahlavi, leaves the country.
Revolutionary leader Ayatollah Ruhollah Khomeini makes a triumphant return from exile in Paris on February 1.
Ten days later, the shah's government falls. Public radio hails "the end of 2,500 years of despotism".
An Islamic republic is proclaimed on April 1.
- US hostage crisis-
Radical students take 52 Americans hostage at the US embassy in Tehran on November 4, 1979, to protest the ex-shah's admission to hospital in the United States.
Washington severs diplomatic relations in 1980. The hostages are only freed on January 21, 1981, after 444 days in captivity.
1980-88: -Iran-Iraq war-
Iraq attacks Iran on September 22 after Iraqi president Saddam Hussein tears up a 1975 treaty on the strategic Shatt al-Arab waterway.
This triggers a gruelling eight-year war that is estimated to have cost hundreds of thousands of lives on both sides.
It ends on August 20, 1988 with a UN-brokered ceasefire.
- 1989: Khamenei takes over-
Khomeini dies on June 3, 1989. Ayatollah Ali Khamenei, president since 1981, becomes supreme leader.
Moderate conservative Akbar Hashemi Rafsanjani is elected president.
Re-elected in 1993, he orchestrates a relative opening up of the government and post-war reconstruction.
Rafsanjani's reformist successor, Mohammad Khatami, runs up against conservative opposition during his two terms from 1997 to 2005.
In 1999, the government faces the biggest protests since 1979, pitting pro-Khatami students against the police.
- 2002: 'Axis of evil' -
US president George W. Bush names Iran as part of an anti-American "axis of evil" with Iraq and North Korea, accusing it of supporting terrorism.
- 2005: Ahmadinejad era-
Populist Mahmoud Ahmadinejad is elected president in June.
During his tenure, Iran resumes uranium enrichment. That alarms the West, which suspects Tehran of wanting to produce a nuclear weapon, something Iran has consistently denied.
A crackdown on nationwide protests against Ahmadinejad's disputed re-election in 2009 hobbles the reformist movement.
- 2015: Nuclear deal-
The election of moderate cleric Rouhani as president in 2013 marks a warming of relations with Washington and the rest of the world.
Iran reaches a deal on its nuclear programme with world powers, including the United States, on July 14, 2015 after 21 months of negotiations.
It gives Tehran relief from crippling economic sanctions in exchange for limits on its atomic activities.
- 2016: Saudi standoff-
In January Iran's regional rival Saudi Arabia and its allies cut or scale back relations, after the Sunni kingdom's execution of prominent Shiite cleric Nimr al-Nimr which prompted demonstrators to ransack the Saudi embassy in Tehran and its consulate in Mashhad.
- 2018: US quits nuclear deal-
US president Donald Trump on May 8 abandons the nuclear deal and begins reimposing unilateral sanctions on Iran.
A year later Tehran begins gradually stepping back from its own commitments.
- 2020: Top commander killed-
On January 3, a US drone strike kills top Iranian commander Qasem Soleimani in Iraq, heightening fears of a direct confrontation after a string of incidents involving Gulf shipping.
Five days later, Iran launches a volley of missiles at US troops stationed in Iraq, but the standoff later eases.
- 2021: Gulf, Israel tensions-
The Revolutionary Guards in January seize a South Korean-flagged tanker in the Gulf amid a dispute over billions in frozen oil funds, the latest in a series of incidents there. The ship is released in April.
The same month, Iran claims Israel is behind an explosion at its Natanz uranium enrichment plant.
In a surprise move in May, the conservative-dominated Guardian Council disqualifies key establishment figure Ali Larijani from the June 18 presidential election.
It approves a field of candidates dominated by ultraconservatives, with judiciary chief Raisi seen as favourite.