Oribasius or Oreibasius (Greek: Ὀρειβάσιος; c. 320 – 403) was a Greek medical writer and the personal physician of the Roman emperor Julian. He studied at Alexandria under physician Zeno of Cyprus before joining Julian's retinue. He was involved in Julian's coronation in 361, and remained with the emperor until Julian's death in 363. In the wake of this event, Oribasius was banished to foreign courts for a time, but was later recalled by the emperor Valens.