Iran Presidential Election 2017: Here is a brief guide to the world's biggest Shia republic
Iran, the Middle East's second largest power by economy and population, is the Shiite Muslim rival of regional Sunni giant Saudi Arabia.
Tehran: Iran, the West Asia's second largest power by economy and population, is the Shiite Muslim rival of regional Sunni giant Saudi Arabia.
Second biggest economy
Iran has the region's second largest economy after Saudi Arabia. With 79.11 million inhabitants (2015, World Bank), it is also the second most populous country in the West Asia, after Egypt.
A founding member of OPEC, it has the world's fourth-biggest oil reserves and the second-largest gas reserves, after Russia.
In 2014, income per capita was $6,550.
Some economic sanctions imposed on Iran over its nuclear programme have been lifted since mid-January 2016, allowing Tehran to resume oil exports and pick up trade with the European Union.
However, the fall in the price of crude has weighed on the economy.
Unemployment officially stands at 12.5 percent, including 27 percent of young people — which analysts say is an understatement — and foreign investment is only trickling in.
Shiite Muslim power
Iran has an area of 1,648,195 square kilometres (659,278 square miles).
The descendant of the Persian Empire, it was long a monarchy ruled by a shah and dominated by the Pahlavi dynasty from 1925 to 1979.
In January 1979, shah Mohammed Reza Pahlavi was driven out by a popular revolt. Ayatollah Ruhollah Khomeini, a revolutionary cleric who had lived in exile for a decade and a half, made a triumphant return on 1 February.
The shah's government fell 10 days later when public radio announced "the end of 2,500 years of despotism". An Islamic republic was proclaimed on 1 April.
Between 1980 and 1988 Iran fought a war with Iraq in which more than a million people were killed.
Rivalry with Saudis
For centuries, Shiite-majority Iran has competed with Turks and Arabs for regional supremacy. Currently, its main rival is Sunni heavyweight Saudi Arabia.
The two countries have taken opposing sides in wars in Syria and Yemen.
In Syria, Tehran backs the regime of President Bashar al-Assad, a member of the minority Alawite community, against Sunni rebels supported by Riyadh.
In Yemen, Saudi Arabia fights in support of pro-government forces against Iran-backed rebels and their allies.
Conservatives, reformers, moderates
After Khomeini died in 1989, Ayatollah Ali Khamenei, president since October 1981, became supreme leader.
Moderate conservative Akbar Hashemi Rafsanjani was elected president and orchestrated economic reforms.
After eight years of rule by reformist president Mohammad Khatami (1997-2005), hardliner Mahmoud Ahmadinejad took office in 2005. His re-election in June 2009 sparked a massive political crisis and a crackdown on nationwide protests that decimated the reformist movement.
Historic nuclear accord
After taking office on 3 August, 2013, President Hassan Rouhani, a moderate cleric, relaunched formal negotiations with major powers on Iran's nuclear programme.
An historic accord was signed on 14 July, 2015 and implemented on 16 January 2016, bringing a 13-year-long dispute to a close.
Terms of the accord stipulate that Tehran will not try to build a nuclear bomb, an ambition it has always denied. In exchange, many international sanctions were lifted although remaining US sanctions continue to stifle trade.
The highest political authority is the supreme leader, who has the final say on all national issues.
The president, elected for four years by universal suffrage, nominates the government.
The Assembly of Experts is a body of elected clerics that oversees the functions of the supreme leader. Constitutionally, it has powers to select and even dismiss the leader.
Parliament's powers are limited when compared to other institutions, and it is vetted by the Guardian Council.
The Expediency Council is Iran's top political arbitration body, tasked with resolving disputes between parliament and the Guardian Council and of advising the supreme leader.
The Revolutionary Guards are the elite arm of the country's military, and deeply embedded in Iranian political and economic life.
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