The so-called Kitâb Hurûsiyûs is an Arabic translation and reworking of the famous Historiae adversus paganos by the Latin historian Paulus Orosius, which was the product of Christian and Muslim authors working together at the court of the Andalusian caliph al-H· akam II al-Mustans· ir. This book acted as a new gateway to the Graeco-Roman world for medieval Islamic culture, and its influence on Islamic historical knowledge was very strong (it was used and quoted by several important Arabic historians and geographers). The English translation and commentary of this text constitute a useful tool for further studies on the subject and, more in general, for a reflection on the topic of the Arabic vision of Greco-Roman history.