Pietro Damiani, an Italian prelate and saint of the Roman Catholic church, born in Ravenna about 1000, died at Faenza, Feb. 22, 1072. While young he entered the monastery of Font' Avellana, of which he became abbot in 1041, and in 1057, greatly against his own will, was raised by Pope Stephen IX. to the rank of cardinal-bishop of Ostia. He persuaded the simoniacal Benedict X. and the antipope Cada-loiis to lay aside their pretensions; he vigorously supported the reforms of which Hilde-brand (Gregory VII.) was the prime mover, and he was in consequence persecuted by the disorderly clergy of Milan, to whom he was sent as legate. In 1062 he withdrew to his solitude at Font' Avellana, but the next year was sent to France by Alexander II. to investigate the charges of simony against the French clergy. In 1069 he went on a mission to Germany to oppose the application of Henry IV. for a divorce, and succeeded in dissuading that sovereign from his intentions. In 1071 he left his monastery again to restore order in Ravenna, the archbishop of which city had been excommunicated.

There are many editions of his writings, comprising sermons, lives of saints, treatises on church attairs, and a work on the abuses of the clergy.