27 *Kayhan Barzegar is a faculty member and chair of the Department of Political Science and International Relations at the Science and Research Branch of the Islamic Azad University. He is also the director of the Institute for Middle East Strategic Studies (IMESS) in Tehran. (barzegar@cmess.ir) **Masoud Rezaei holds a Ph.D. in International Relations from the Islamic Azad University, Isfahan Branch. He is currently a visiting research fellow at the Institute for Middle East Strategic Studies (IMESS) in Tehran. (rezaei@cmess.ir) Discourse: An Iranian Quarterly , Vol. 11, No. 3, Winter 2017: 27-54. Kayhan Barzegar* Masoud Rezaei** Abstract What is Ayatollah Khamenei’s strategic thinking, and how does it shape and influence Iran’s foreign policy, military and national security strategy? This article studies the theoretical and conceptual dimensions of Ayatollah Khamenei’s foreign policy and strategic thinking, including his aims and principles, approaches, behaviors, decisions, and incentives, as the Islamic Republic of Iran’s commander-in-chief of armed forces. The authors strive to explain how the political and military doctrine of Iran’s Supreme Leader is designed to increase the country’s relative security. They argue that Iran’s leader tries to neutralize challenges caused by new changes that have occurred in Iran’s immediate security sphere through activating patterns related to active deterrence. Thus, for him, sufficient military power can only be obtained by maximizing security. This way of thinking can best be explained by defensive realism theory. In this context, four dimensions of this theory i.e., balance of power, balance of threat, interconnected security, and offense-defense approach are discussed in the thoughts of Iran’s leader. The authors also hold that the ethical aspect of Ayatollah Khamenei’s strategic thinking, based on the principles of Islamic international relations, gives realism in the Middle East a critical approach. Keywords: Ayatollah Khamenei, Iran’s N ational Security, Defensive Realism, Relative Security, Balance of Power, Offense-Defense Approach Ayatollah Khamenei’s Strategic Thinking