[2][3] Born in Calabria in a locality described as being the "closest to Sicily",[2] Fantinus was introduced as a child to Saint Elias the Cave-Dweller.

Fantinus lived a life of extreme asceticism, eating only raw vegetables, and occupying his time copying manuscripts.

He subsequently convinced his aged parents, as well as his two brothers, Luke and Cosmas, and sister Caterina, to enter the monastic life.

Though a hermit, he often returned from the wild in order to serve as a guide and spiritual teacher to disciples, such as Nilus the Younger and Nicodemus of Mammola.

Fantinus is said to have made the sign of the cross over a container filled with seawater and miraculously converted it into drinkable water.