We find the majority of what we know of Saint Hilarion from a biography written by Saint Jerome in roughly the year 390. In it, we learn that Saint Hilarion was born roughly in the year 291 AD in the town of Thabatha, Syria Palestina. He studied Grammar in Alexandria and grew up with two parents who were not Christian.
During his studies at Alexandria, he heard the Gospel and converted to Christianity. At the young age of 15, he began to learn and study under Saint Anthony of Egypt for two months in the desert. Shortly after returning home, his parents died and left a sizable inheritance; he gave this money to the poor and to his brothers before leaving for the desert.
He left for the desert southwest of Majoma and lived a nomadic life. He carried only a shirt, a cloak and a rough blanket given to him by Saint Anthony. Because of the dangerous territory (it was known as an area of bandits and thieves), Saint Anthony had to constantly move from place to place. Saint Jerome writes that he was beset with terrible temptations:
So many were his temptations and so various the snares of demons night and day, that if I wished to relate them, a volume would not suffice. How often when he lay down did naked women appear to him, how often sumptuous feasts when he was hungry! (Jerome, Life of St Hilarion, 7)
Near the city of Deir al-Balah, he built himself a small hut that was so spartan it was described by Saint Jerome as resembling more of a tomb than a house. Saint Jerome emphasizes Saint Hilarion's proselytizing the Saracens and his many miracles among the sick and demoniacs. Among the many miracles attributed it is said that when visited by a woman who had been barren for 15 years, he laid hands on her and she was cured. He healed a paralyzed charioteer, expelled demons and cured a child of an illness that should have killed him.
As his fame spread, more and more visitors came to the small hut where he had lived. It had turned into a small monastery itself, depriving Saint Hilarion of his solitude. He left quickly, travelling place to place in an effort to find solitude. It is written that he travelled to Thebes, North Africa, Sicily and eventually Cyprus. It was in Cyprus that he died roughly at 80 years old in the year 371 AD.
His feast day is celebrated on October 21st in the Roman Catholic Church.