William was born in 11th-century Italy to a noble family. He was orphaned as an infant and raised by relatives. At the young age of 14, he made a pilgrimage to Santiago de Compostela in Spain, and decided to devote his life to God as a hermit.
He returned to Italy and lived as a hermit for two years at Monte Solicoli, where he was credited with healing a blind man. At Monte Vergiliano, his reputation for holiness attracted many disciples, and in 1119, he established a monastery with a Rule based on the Benedictines.
Five other houses were formed during his lifetime, but only the original survives today. He died June 25, 1142 of natural causes.