Didymus of Alexandria, d. c.396, Greek grammarian and theologian, also called Didymus the Blind. His treatise On the Holy Ghost was translated by St. Jerome, who studied briefly with him. Although Didymus had been trusted with teaching theology by St. Athanasius, he was condemned for Origenism by the Third Council of Constantinople and the Second Council of Nicaea.

Didymus Chalcenterus, fl. 1st cent. B.C., Hellenistic Greek grammarian and expositor. Famous for his prodigious literary output, he supposedly produced over 3,500 works. He collated much of the work of the Alexandrian critics, and though only fragments of his own work are extant, he is probably the source of many surviving classical commentaries.

Didymus: see Thomas, Saint.