Bishop of Altino
Saint Heliodorus was born at Dalmatia, a Roman Province northeast of the Adriatic Sea, which was also the native land of Saint Jerome. He soon sought out that great Doctor, not only to follow his advice in matters relating to Christian perfection, but also to profit by his deep learning. The life of a recluse held great attractions for him, but to enter a monastery it would have been necessary to leave his spiritual master and director, a sacrifice he was not prepared to make. He therefore remained in the world, though not part of it, and following the example of the holy anchorites, passed his time in prayer and devout reading. He accompanied Saint Jerome on his voyage to the Holy Land, visiting the various churches of the Orient, and remained with him for a time, but a desire to revisit his native land and to see his parents once more drew him back to Dalmatia. Saint Jerome tried to persuade him to remain with him, and Heliodorus was intending to return, as soon as he had fulfilled the duties he owed his parents.
Finding his absence had grown prolonged, and fearing that love for his family and attachment to worldly things might lure him from his vocation, Saint Jerome wrote him an earnest letter. He exhorted his good disciple to break entirely with the world and to consecrate himself to the service of God. But the Lord, who disposes all things, had a mission of activity reserved for His servant. After the death of his mother, Heliodorus went to Italy and soon was remarked for his eminent piety. He was made Bishop of Altino, and became one of the most distinguished prelates of an age fruitful in great men. He sustained the Catholic faith against the Arian heresy, assisting at the Council of Aquilea in northeastern Italy, called for that purpose in 381. Saint Jerome never forgot his former student, and in one of his letters testifies that he was a bishop who lived in his episcopal dignity with as much fervor and regularity as in a monastery. Saint Heliodorus died about the year 390.
Little Pictorial Lives of the Saints, a compilation based on Butler's Lives of the Saints, and other sources by John Gilmary Shea (Benziger Brothers: New York, 1894).