In a world where most nations are multinational states, ethnic issues often become serious trans-national concerns, as they could potentially lead to international conflicts. This article first puts ethnic issues in the perspective of contemporary international relations through identifying three different manifestations of international ethnic disputes. Then the article examines ethnic issues in the context of international law and norms, especially focusing on key concepts of national self-determination, secession, intervention, and state sovereignty. Finally it makes a presentation on the main conceptualizations of ethnic issues in international relations.