The water crisis is one of the most fundamental challenges of the 21st century, especially in the Middle East. The Tigris and Euphrates rivers, which have long been the cradle of human civilizations, have today become the subject of political, economic, and environmental disputes between the countries of Turkey, Iraq, and Syria. The Turkish GAP project, as the largest dam construction project in this country, although designed with developmental and economic goals, has had serious and widespread consequences for the environment and water security of downstream countries. This study, using a descriptive-analytical method and based on library and documentary sources, examines the legal dimensions of the GAP project in the light of international environmental law. The results show that Turkey's unilateral policies violate the fundamental principles of international environmental law, including the principle of fair and reasonable use, the principle of no harm, and the principle of cooperation between states. Continuing this process without international supervision and cooperation could have irreparable social and security consequences for the region, in addition to the environmental crisis.