Aristobulus of Cassandreia (Ancient Greek: Ἀριστόβουλος ὁ Κασσανδρεὺς; c. 375 BC – 301 BC), Greek historian, son of Aristobulus, probably a Phocian settled in Cassandreia,[1][2][3] accompanied Alexander the Great on his campaigns. He served throughout as an architect and military engineer[4] as well as a close friend of Alexander, enjoying royal confidence, and was entrusted with the repair of the tomb of Cyrus the Great in Pasargadae. He wrote an account, mainly geographical and ethnological.[5] It survives only in quotations by others, which may not all be faithful to the original. His work was largely used by Arrian. Plutarch also used him as a reference.[5]