"Fundamental Concepts in International Public Law" represents the most recent attempt to create an instructional textbook aimed at undergraduate and postgraduate students. It is a collective effort that seeks to capture the authors' experience from teaching International Law in Greece and France.

In this sense, the present book is intended to meet teaching needs as a supplement to classroom instruction. At the same time, it reflects the authors' personal perspective and involves the reader in a continuous discussion about the foundations of International Law, as well as the functioning and particularities of the international legal order.

It follows the classic structure of books dealing with this topic, beginning with the historical, methodological, and theoretical pathways of International Law, its subjects and sources, and concluding with the legal order established by the United Nations. This thematic sequence unfolds through dynamic tensions and debates around the subjects and sources of International Law, which also reflect on the relationships developed between different legal orders.

The discussion around International Law, its nature, function, and effectiveness, is constantly enriched with new ideas and produces knowledge and questioning. The authors hope that this book will serve as a useful guide for students to maximize their benefits from engaging with International Law and to develop a more comprehensive legal education.