Euclid's Elements is one of the canonical texts that shaped our cultural heritage. It was translated from Greek into Arabic and from Arabic into Hebrew and Latin. There is little agreement about the textual history of the Arabic translations. The present book offers for the first time a critical edition of two Hebrew translations of Books I-II, by Moses Ibn Tibbon and by "Rabbi Jacob". A serious attempt is made to learn from the Hebrew translations also about the history of the Arabic text. The edition of Ibn Tibbon's translation is accompanied by an Arabic text which was probably its source. Rabbi Jacob's translation is compared to the Latin translation ascribed to Adelard of Bath, probably based on the same Arabic tradition.