The following outline is provided as an overview of and topical guide to Iran: Iran – sovereign country located in Southwest Asia and the Middle East. Iran is bound by the Gulf of Oman and the Persian Gulf to the south and the Caspian Sea to its north. Shi'a Islam is the official religion, and Persian is the official language. Iran's population is about 83,500,000; and is the 18th largest country in the world in terms of area at 1,648,195 square kilometres (636,372 sq mi). Iran is home to one of the world's oldest continuous major civilizations, with historical and urban settlements dating back to 4000 BC. Throughout history, Iran has been of geostrategic importance because of its central location in Eurasia and is a regional power. The political system of Iran, based on the 1979 Constitut