This research aims to conduct a comparative study of civil laws related to nationality and the rights of foreign nationals in three countries: Iran, Turkey, and Germany. Given the legal, cultural, and historical differences among these countries, a comparative analysis can help better understand the legal challenges in the fields of nationality and immigration. The present study examines the concepts of nationality, conditions for acquiring citizenship, the rights and obligations of foreign nationals, as well as the status of marriage and residency in these countries. In Iran, nationality is based on the principle of jus sanguinis (right of blood), and the process of acquiring it is complex and influenced by cultural and religious factors. Additionally, there are significant restrictions on renouncing citizenship and dual nationality. In Turkey, nationality is generally independent of religion and is determined based on republican laws. Turkey has adjusted its immigration policies to attract foreign investors and labor. In Germany, nationality is defined according to modern legal principles aligned with European Union standards. Over recent decades, Germany has facilitated the acquisition of citizenship for immigrants by revising its immigration policies. The findings of this research reveal significant differences in the nationality laws of these countries, stemming from their historical, legal, and political backgrounds. These differences impact the rights of immigrants, residency policies, and international interactions. Given the trends of globalization and the increase in international migration, reviewing and reforming nationality laws is of particular importance. This study attempts to provide a comparative analysis, offering a framework for better understanding these issues and proposing appropriate solutions to improve the legal status of immigrants in Iran.