Oribasius was an eminent Greek physician of the 4th century AD, born in Pergamon. He studied in Alexandria and became the personal physician of the Roman emperor Julian the Apostate. He is mainly known for his monumental medical encyclopedia, "Collectiones Medicae" (Medical Collections), an exhaustive compilation of earlier Greek medical knowledge consisting of about 70 works, of which only fragments survive. His work was a fundamental source of medical knowledge for centuries.