The prerequisite for any kind of national development and prosperity is the existence of political stability, under which social forces can coordinate their energy and creativity by forming and achieving coalitions and unity, and pave the way for achieving national goals. Several factors can cause political instability and prevent society from growing, flourishing, prosperity, and national vitality. One of these factors, according to historical, political, and social experiences, is the existence of an ethnic identity crisis. Since Iran is a multi-ethnic country that includes Kurds, Arabs, Lors, Azeris, Turkmens, Baluchis, and Persians, this study focuses on the ethnic identity crisis as a political threat in the Islamic Republic. First, ethnicities are identified and whether these ethnicities suffer from an ethnic identity crisis or not. Then, if there is an ethnic identity crisis, has this crisis had any effect on political stability? To achieve these goals, a descriptive-analytical research method was used, and the desired information was examined through a library study (books, articles, and journals) to test the hypothesis of the relationship between the ethnic identity crisis and political instability in the Islamic Republic of Iran. The results indicate that, first, the ethnic identity crisis existed among a number of ethnicities in Iran before and after the Islamic Revolution. Second, this ethnic identity crisis has been the basis for political instability in the political system of the Islamic Republic at certain times. Considering the above-mentioned findings, although one cannot be reductionist in analyzing the factors underlying political instability, the ethnic identity crisis can also be considered as one of the important factors underlying political instability. The findings of this study show that managing the ethnic identity crisis through comprehensive socio-cultural policies and strengthening inter-ethnic dialogue can help reduce political tensions. Also, paying attention to the cultural and linguistic rights of ethnic groups within the framework of the constitution and implementing logically balanced development programs can pave the way for national cohesion and sustainable political stability. Finally, this research emphasizes the necessity of adopting a comprehensive and multidimensional approach in analyzing the phenomenon of political instability in multiethnic countries.