Acacius may refer to:
- Saints
- Agathius, also known as Acacius of Byzantium (d. 303), Centurion of the Imperial Army. Feastday: May 8
- Saint Acacius, 4th century Armenian priest. Feastday: November 27
- Acacius of Amida (fl. 400–425), Mesopotamian bishop. Feastday: April 9
- Acathius of Melitene, 3rd century bishop, venerated by the Eastern Orthodox Church. Feastday: March 31
- Saint Acacius, leader of the Ten thousand martyrs. Feastday: 22 June
- Other uses
- Acacius the grammarian from Caesarea. A friend of Libanius (314–394).
- Acacius of Caesarea (d. 366), aka "the One-Eyed", bishop in Caesarea, opponent of St. Cyril of Jerusalem
- Acacius of Beroea (d. 437), Syrian bishop
- Patriarch Acacius of Constantinople (d. 489), Eastern Orthodox, active in the monophysitism controversy
- Acacius (Nestorian Patriarch) (d. 496), Patriarch of the Church of the East
- Acacius, father of Theodora (6th century) (500–548), empress of the Byzantine Empire
- Acacius, Byzantine proconsul of Armenia Prima (First Armenia), c. 536-539
- Acacius, Byzantine military officer in Alexandria, c. 539-540
- Acacius, Byzantine imperial curator in the 560s
- Acacius, Byzantine imperial representative, active c. 573