GUGLIELMO of HIRSAU, Blessed. — Born in Bavaria; died 4 July 1101 at Hirsaú. As a child he was offered as an oblate to the monastery of St Emmeram in Ratisbon; in 1069 he was called by the monks of the restored Hirsaú to be their abbot, though he did not receive ordination until after the death of his predecessor Frederick, who had been unjustly deposed. Under his prudent and moderate rule, Hirsaú began to flourish again. G. worked tirelessly to obtain from Henry IV and Pope Gregory VII—whom he visited in person—full exemption for his monastery, which he governed until 1075.
Following the model of the *Constitutiones Cuniacenses*, he composed the *Constitutiones Hirsauenses* (cf. M. Fischer, *Studien zur Entstehung der Hirsauer Konstitutionen*, Tübingen 1910). The number of monks grew so greatly that a second monastery had to be built (1083–92), and numerous monastic colonies were sent to Erfurt, Magdeburg, Styria, and Carinthia. He was one of the promoters of the Oblates’ Institute within the Benedictine Order. After meeting Pope Gregory VII and receiving the visit of his legate Bernard of Marseilles, G. and his monks became vigorous defenders of the Gregorian Reform in Germany. A man of wide learning, he left several works: *Dialogi de Musica* (PL 150, 1147–78; critical ed. by H. Müller, Frankfurt 1883) and *Astronomia* (only the prologue printed: PL 150, 1639–42). Until the decline of the monastery of Hirsaú, G. enjoyed public veneration. Feast: 5 July.