Donatus Magnus was a Berber Christian and leader and bishop of a schismatic Christian group in North Africa during the first half of the fourth century. His name became identified with the schismatic group, the Donatist, and to its heresy.
Little is known of his early life. He appeared in history as Bishop Donatus of Casae Nigrae the successor in 313 to Majorinus, the schismatic Bishop of Carthage. He has been also referred to as Donatus the Great (Donatus Magnus).
In 316, Donatus represented the schismatics when their dispute with Caecilian over the see of Carthage was presented before Constantine I in Milan. They did not recognize Caecilian as Bishop of Carthage.