Iran , also known as Persia , officially the Islamic Republic of Iran , is a sovereign state in Western Asia. It is bordered to the northwest by Armenia, the de facto Nagorno-Karabakh Republic, and Azerbaijan; to the northeast by Turkmenistan; to the east by Afghanistan and Pakistan; to the south by the Persian Gulf and the Gulf of Oman; to the north by the Caspian Sea; and to the west by Turkey and Iraq. Comprising a land area of 1,648,195 km2 (636,372 sq mi), 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 with both a Caspian Sea and an Indian Ocean coastline. The country’s central location in Eurasia and Western Asia, and its proximity to the Strait of Hormuz, make it of great geostrategic importance. Tehran is the country’s capital and largest city as well as its leading economic center.