Atto of Vercelli or Atto II (c. 885–961) was a Lombard who became bishop of Vercelli in 924. He served as Grand Chancellor to Hugh of Provence and Lothar II, both Kings of Italy in the 10th century. During his time as bishop, Atto was known for his devotion to the welfare of the people in his diocese, both temporal and spiritual, and the vigor with which he attacked ecclesial corruption. He wrote several works in his lifetime. His major compositions include Polypticum, a treatise on the morality of Italy in the day; De pressuris ecclesiasticis, an essay regarding ecclesiastical authority; and the Capitulare, a collection of canon law from his area, including some of the False Decretals, augmented by his own additions of ecclesiastic law. A small selection of his sermons survives in written form. He died in 961.