Iran (Persian: ايران [ʔiˈɾɒn] ), officially the Islamic Republic of Iran and formerly known internationally as Persia until 1935, is a country in Central Eurasia, located on the northeastern shore of the Persian Gulf, northwestern shore of the Gulf of Oman, and the southern shore of the Caspian Sea. Both "Persia" and "Iran" are used interchangeably in cultural context; however, Iran is the name used officially in political context. The name Iran is a cognate of Aryan, and means "Land of the Aryans".

The 18th largest country in the world in terms of area at 1,648,195 km², Iran has a population of over seventy million. It is a country of special geostrategic significance due to its central location in Eurasia. Iran is bordered on the north by Armenia, Azerbaijan and Turkmenistan. As Iran is a littoral state of the Caspian Sea, which is an inland sea and condominium, Kazakhstan and Russia are also Iran's direct neighbors to the north. Iran is bordered on the east by Afghanistan and Pakistan, on the south by the Persian Gulf and the Gulf of Oman, and on the west by Turkey and Iraq. Tehran is the capital, the country's largest city and the political, cultural, commercial, and industrial center of the nation. Iran is a regional power, and holds an important position in international energy security and world economy as a result of its large reserves of petroleum and natural gas.

Iran is home to one of the world's oldest continuous major civilizations, with historical and urban settlements dating back to 7000 BC. The first Iranian dynasty formed during the Elamite kingdom in 2800 BC. The Iranian Medes unified Iran into an empire in 625 BC. They were succeeded by three Iranian Empires, the Achaemenids, Parthians and Sassanids, which governed Iran for more than 1000 years. 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 blossoming of Persian literature, philosophy, medicine, astronomy, mathematics and art became major elements of Muslim civilization and started with the Saffarids and Samanids. Iran was once again reunified as an independent state in 1501 by the Safavid dynasty — who promoted Twelver Shi'a Islam as the official religion of their empire, marking one of the most important turning points in the history of Islam. "Persia's Constitutional Revolution" established the nation's first parliament in 1906, within a constitutional monarchy. Iran officially became an Islamic republic on 1 April 1979, following the Iranian Revolution.

Iran is a founding member of the UN, NAM, OIC and OPEC. The political system of Iran, based on the Constitution, comprises several intricately connected governing bodies. The highest state authority is the Supreme Leader. Shia Islam is the official religion and Persian is the official language.