Acacius (died 489) is the Ecumenical Patriarch of Constantinople from 471 to 489.

Acacius is practically the first prelate throughout the Eastern Orthodoxy and renowned for ambitious participation in the Chalcedonian controversy Acacius advises the Byzantine emperor Zeno to issue the Henotikon edict in 482, in which Nestorius and Eutyches are condemned, the twelve chapters of Cyril of Alexandria accepted, and the Chalcedon Definition ignored.

This effort to shelve the dispute over the orthodoxy of the Council of Chalcedon is quite in vain.

Pope Felix III sees the prestige of his see involved in this slighting of Chalcedon and his predecessor Leo’s epistle.

He condemns and deposes Acacius, a proceeding which the latter regards with contempt, but which involves a schism between the two sees that lasts after Acacius’s death.

The Acacian schism lasts through the long and troubled reign of the Byzantine emperor Anastasius I, and is only healed by Justin I under Pope Hormisdas in 519.

The Coptic Orthodox Church celebrates The Departure of St. Acacius, Patriarch of Constantinople on the 30th of the Coptic month of Hatour.