Abstract: The Caspian Sea basin is one of the most important oil-rich regions in the world and its peripheral countries together have 51% of oil reserves and 15% of world gas reserves. For years, the former Soviet socialist system was the sole producer of oil and gas from the Caspian Sea. After the collapse of the Soviet Union, five countries, Iran, Azerbaijan, Turkmenistan, Kazakhstan and Russia, were able to exploit these resources. From the US point of view, the Caspian Sea is one of the two most important regions that can meet the growing global demand for energy. And for that reason, that power must be effectively controlled. There are various estimates for Caspian oil reserves, from a maximum of 522 billion barrels to a minimum of 02 to 02 billion barrels. 02 billion barrels is the figure used by most companies in the region. He mentioned the importance of gas energy for the Caspian-Central Asia, but this is not the case in practice. The gas reserves of both countries are located in parts far from the Caspian region. Some American thinkers in the new geopolitics have called the combination of the two important energy regions of the Persian Gulf and the Caspian Sea as the two important sources of energy the strategic energy ellipse "The Ellipse Energy Strategic" that surrounds Iran. Despite having a common geopolitics, the countries of this region have different attitudes. The question now is "What are the factors influencing the geopolitical developments of the Caspian littoral countries?" Population, economy and so on. In this article, the geopolitical importance of the Caspian Sea countries, especially the Islamic Republic of Iran, is examined.