Dalmatius, Dalmatus, or Dalmatos (Ancient Greek: Δαλμάτος; died AD 440) was archimandrite of the Dalmatian Monastery in Constantinople.
He also held the title Archimandrite of the Monasteries, making him the city's chief monk.
Experiencing a call to monastic life, he received instruction from Isaac of Dalmatia.
[2] Like most of the city's monks, he was an opponent of the Nestorian heresy, and he played an important role in the downfall of Nestorius.
Following Cyril of Alexandria's instructions, Dalmatius led an army of monks to the palace of Theodosius II, and shouted abuse against him, because he had sided with the Nestorians and annulled the First Council of Ephesus.