The Abbey of the Saints Nazario and Celso (Italian: Abbazia dei Santi Nazario e Celso) is a monastic complex in the municipality of San Nazzaro Sesia, Piedmont, northern Italy. It consists of a city wall with circular corner towers, a high Romanesque bell tower, a church in Lombard Gothic style and a cloister with a group of 15th-century frescoes dedicated to the stories of St. Benedict.