Acacius is a masculine given name which may refer to:

• Acathius of Melitene (died c. 251), Bishop of Melitene, venerated by the Eastern Orthodox Church
• Agathius, also known as Acacius of Byzantium (died 303), martyred Cappadocian Greek centurion of the imperial army
  • An early Church of St Acacius existed at Constantinople, possibly connected with this martyr.
• Acacius of Sebaste (died c. 304), Armenian priest
• Acacius (died 320), Roman soldier and one of the Forty Martyrs of Sebaste
• Acacius of Amida, Bishop of Amida, Mesopotamia (400–425)
• Acacius of Constantinople (died 489), Ecumenical Patriarch of Constantinople, Oriental Orthodox saint engaged in the Christological controversy
• Saint Acacius, leader of the Ten thousand martyrs (Roman soldiers who converted to Christianity and were crucified in Armenia), according to medieval legend
• Acacius the Younger (died 1730), Greek Orthodox monk who lived on Mount Athos

• Acacius the grammarian from Caesarea; 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
• Acacius of Seleucia-Ctesiphon (d. 496), Patriarch of the Church of the East
• Acacius, father of Theodora (6th century) (500–548), empress of the Byzantine Empire
• Acacius (proconsul), Byzantine proconsul of Armenia Prima (First Armenia), c. 536-539
• Acacius (Alexandria), Byzantine military officer in Alexandria, c. 539-540
• Acacius (curator), Byzantine imperial curator in the 560s
• Acacius (son of Archelaus), Byzantine imperial representative, active c. 573

• Acacia (disambiguation)