Altmann of Passau was a 11th-century German bishop who led the diocese of Passau from 1065 until 1091. Born into Saxon nobility in Westphalia, he was educated at the cathedral school in Paderborn and served as a court chaplain to Emperor Henry III. He is primarily recognized for his intense commitment to the Gregorian reforms and his active support for Pope Gregory VII during the Investiture Controversy. As a monastic reformer, he established several new religious houses and worked to revitalize existing monasteries throughout the German lands and Austria.