PIUS I. Hardly anything is known with certainty respecting Pius I., except that he was bishop of Rome from 158 to 167 A.D. He is said to have been born at Aquileia and to have been the son of a certain Rufinus ; it is added that he suffered martyrdom, but, although be is celebrated as a martyr in the breviary, there seems no other evidence for this assertion. A few letters extant under his name are spurious.