Acacius of Caesarea (Greek: Ἀκάκιος; date of birth unknown, died in 366) was a Christian bishop probably originating from Syria; Acacius was the pupil and biographer of Eusebius and his successor on the see of Caesarea Palestina. Acacius is remembered chiefly for his bitter opposition to Cyril of Jerusalem and for the part he was afterwards enabled to play in the more acute stages of the Arian controversy. The Acacian theological movement is named after him. In the twenty-first oration of St. Gregory Nazianzen, the author speaks of Acacius as being "the tongue of the Arians".