Benno II (c. 1020 – 27 July 1088) was Bishop of Osnabrück from 1068 until his death. He served as a close advisor and architect of Emperor Henry IV. In 1080 he founded the Benedictine abbey of Iburg Castle.
He was born at Löhningen (today part of Ühlingen-Birkendorf) in Klettgau, Swabia, the son of a ministerial family. His parents sent him at an early age to the monastic schools of Straßburg and Reichenau where the learned Herman Contractus was then teaching. Together with William I, Archbishop of Strasbourg, he went on a pilgrimage to Jerusalem about 1040.
Having completed his education, he taught for some time at the cathedral school of Speyer in Rhenish Franconia. In 1047 he became teacher at the Benedictine school of Goslar in Saxony and, shortly after, was made headmaster of the cathedral school at Hildesheim, where he reformed the education at the behest of Bishop Azelin. In Speyer, he had contacted the Imperial court of the Salian emperor Henry III. On account of his skill in architecture he was appointed imperial architect and, as such, supervised the construction of numerous castles and churches in the Holy Roman Empire. When the Rhine, which flowed close to the Cathedral of Speyer, threatened to undermine its foundations, Benno saved the structure by changing the course of the river. He and Bishop Azelin of Hildesheim accompanied Henry on a 1051 campaign against King Andrew I of Hungary, whereby Benno distinguished himself in providing the forces' catering. Upon his return he was made provost of Hildesheim, archpriest at Goslar Cathedral and royal vicedominus at the Imperial Palace.