Iran - a country in Southern and Western Asia. The name "Iran", which in Persian means "Land of the Aryans", has been in use natively since the Sassanian era. It came into use internationally in 1935, before which the country was known to the Western world as Persia Both "Persia" and "Iran" are used interchangeably in cultural contexts; however, "Iran" is the name used officially in political contexts.
Iran is home to one of the world's oldest civilizations. The first dynasty in Iran formed during the Elamite kingdom in 2800 BC. The Iranian Medes unified Iran into an empire in 625 BC. They were succeeded by the Iranian Achaemenid Empire, the Hellenic Seleucid Empire and two subsequent Iranian empires, the Parthians and the Sassanids, before the Muslim conquest in 651 AD. Iranian post-Islamic dynasties and empires expanded the Persian language and culture throughout the Iranian plateau. Early Iranian dynasties which re-asserted Iranian independence included the Tahirids, Saffarids, Samanids and Buyids.
The emergence in 1501 of the Safavid dynasty, which promoted Twelver Shia Islam as the official religion of their empire, marked one of the most important turning points in Iranian and Muslim history. The Persian Constitutional Revolution established the nation's first parliament in 1906, within a constitutional monarchy. In 1953 Iran became an authoritarian regime, following a coup d'état instigated by the UK and US. Growing dissent with foreign influence culminated during the Iranian Revolution which led to establishment of an Islamic republic on 1 April 1979.
Iran is a founding member of the UN, NAM, OIC and OPEC. The political system of Iran, based on the 1979 constitution, comprises several intricately connected governing bodies. The highest state authority is the Supreme Leader.