In this work, Khaled Ramadan Bashir presents and discusses the precise nature of Mohammad Al-Shaybnai’s contribution to Siyar (Islamic International Law). He compares his work to other great contributions on international law made by renowned scholars including Augustine, Gratian, Aquinas, Vitoria and Grotius. Bashir affirms the view that Al-Shaybnai made a major contribution to the field of International law, which was unparalleled until Grotius wrote The Law of War and Peace. To date, Al-Shaybnai’s Siyar is still a cornerstone of the Islamic perspective of international law.