"Theory of International Law" is the main scientific work of a well-known specialist in international law, professor of the law faculty of Moscow State University named after M.V. Lomonosov G.I. Tunkin (1906-1993). In it, Tunkin outlined and substantiated the theory of coordination of the will of states. In parallel with this, the book addresses the issues of the relationship of international law with foreign policy and diplomacy, international legal responsibility of the state, the law of international organizations, etc. This book is intended for students, graduate students, teachers and researchers involved in international relations.