Saint Achillius of Larissa, also known as Achilles,[1] Ailus,[2] Achillas,[1] or Achilius[3] (Greek: Άγιος Αχίλλειος, Ágios Achílleios) (died 330 AD), was a 4th century bishop of Larissa and one of the 318 persons present at the First Council of Nicaea.

Achillius is mainly remembered for his vehement defense of orthodoxy during the Council of Nicea and a miracle he performed in testimony against Arianism.

Then the saint continued: 'And if the Son of God is equal to the Father, as we believe, then let oil flow from this stone.'

[5] The 1910 Catholic Encyclopedia makes issue to reference Achillius in its article about the bishopric of Larissa.

When Samuel, Emperor of Bulgaria, conquered Thessaly, he translated the relics of Achillius to Prespa, to an island in a lake that was subsequently named after the saint.