Iran ( or ; ), also known as Persia ( or ), officially the Islamic Republic of Iran ( ), is a country in Western Asia. It is bordered to the northwest by Armenia, the de facto Nagorno-Karabakh, and Azerbaijan; with Kazakhstan and Russia across the Caspian Sea; to the northeast by Turkmenistan; to the east by Afghanistan and Pakistan; to the south by the Persian Gulf and the Gulf of Oman; and to the west by Turkey and Iraq. Comprising a land area of , it is the second-largest country in the Middle East and the 18th-largest in the world. With 78.4 million inhabitants, Iran is the world's 17th-most-populous country. It is the only country that has both a Caspian Sea and an Indian Ocean coastline. Iran has long been of geostrategic importance because of its central location in Eurasia and Western Asia, and its proximity to the Strait of Hormuz.

The name of Iran derives immediately from 3rd-century Sassanian Middle Persian , Pahlavi 'yr'n, where it initially meant "of the Iranians", but soon also acquired a geographical connotation in the sense of "(lands inhabited by) Iranians". In both geographic and demonymic senses, eran is distinguished from its antonymic aneran, meaning "non-Iran(ian)".