The Monk of Clonmacnoise is the anonymous author of the Old Irish homilies and passions preserved in the Leabhar Breac and related manuscripts — the vernacular sermons on the Passion, the Resurrection, the Harrowing of Hell, the apostles and the martyrs, with the Life of Ciarán of Clonmacnoise. Written in the eleventh and twelfth centuries, they are the chief corpus of early Irish preaching.