This book delves into the connections between the Islamic Republic of Iran and the countries of the southern Caucasus region following the 1979 revolution. It focuses on their political, economic, and cultural interactions and elaborates on Iran's foreign policy principles, discourses, and significant decision-making institutions. It also addresses the process of nation-state building in the southern Caucasus, the challenges involved, and the geopolitical and strategic importance of this area for Iran. Factors influencing the relations are scrutinised, alongside an evaluation of the proposed accession of the Republic of Azerbaijan into Iran, based on insights from Hashemi Rafsanjani's diary. The work further investigates the legal framework of the Caspian Sea and Aras River, examines the strategic implications of the 2020 Nagorno-Karabakh conflict for Iran and other relevant actors, and analyses the repercussions of the Ukraine war on transportation routes. This book will help researchers of the Middle East and the Caucasus better understand Iran's relations with the region.