The Egyptian priest Manetho of Sebennytos, the author of a work on the history of Egypt written in Greek in the first half of the III century B.C., gave in its second tomos (book) dealing with the events of the second millennium B.C. the information on the conquests of the king Sesostris of Dynasty XII, the historical Senwosret III. This evidence was transmitted by George Synkellos, who followed Julius Africanus, Eusebius of Caesarea, and Eusebius’ Armenian version. These authors reproduced an epitome of Manetho’s text from the end of the Hellenistic period. The analysis of these testimonies and their comparison with the data from the ancient tradition allows us to conclude that, apparently, epitomators accurately reproduced the essence of Manetho’s narration. Moreover, Manetho named the territories of Sesostris’s conquests, described his appearance, and indicated the duration of his reign. These reports are close to the accounts of Hecataeus of Abdera, the court historiographer of the satrap of Egypt, Ptolemy, son of Lagus. In turn, the information from Hecataeus is known thanks to Diodorus Siculus. Hecataeus’s text was signifi cant for Manetho as a work of offi cial historical writing of the house of Ptolemies. Moreover, it was an extensive and detailed work, and its information about the great conqueror of the distant past was consistent with what was independently known to the Egyptian historian. However, Manetho used the form of the name of this king (Sesostris), introduced not by Hecataeus, but much earlier, by following, apparently due to the established association of this name with military feats. He also determined the place of this king in the dynastic sequence not according to Hecataeus, but following his own information, derived from the hieroglyphic tradition. Besides, Manetho must have shared Hecataeus’ view that the king Sesostris founded the great interregional empire, which united Asia and must have passed under the sway of Assyria by the time of the Hyksos invasion of Egypt.