The Taliban militia forces, with a number of less than seventy-five thousand people, overcame the three hundred thousand-strong Afghan army in eleven days. The people of Afghanistan also experienced the rule of this extremist Islamist group at 1996 to 2001, until the Taliban government fell following the September 11 incident and the US attack on Afghanistan, and the US sought to establish a nation-state in this country. After more than twenty years, the US government decided to withdraw its forces from Afghanistan. With the beginning of the withdrawal of American forces, the Taliban militias succeeded in forming the second Islamic Emirate in this country in the shortest possible time in 2021. The rapid victory of the Taliban raised questions, the most important of which are: First, were these developments a scenario and project designed by the US? Second, what was the reason for the Taliban's rapid victory in Afghanistan and how will their government in the new era be fundamentally different from their government in the previous era? Third, what consequences could the Taliban's re-dominance in Afghanistan have for the Islamic Republic of Iran? Therefore, the purpose of writing this article is to state the reasons for the Taliban's re-emergence in Afghanistan and explain its consequences in the region, especially for the Islamic Republic of Iran, in a descriptive-analytical manner and using library tools including books, newspapers and internet resources.