Bobbio, town, Emilia-Romagna region, northern Italy, in the valley of the Trebbia River, southwest of Piacenza. The ancient Bobium, it became famous when the Irish missionary monk St. Columban (Colombano) founded a monastery there c. 612, after fleeing from what is now Switzerland. He died three years later, but the monastery flourished and became a centre of medieval culture and learning, especially renowned for its great library. The monastery declined in the 15th century, and the library, with its approximately 700 manuscripts from the 10th century, was subsequently dispersed, most of it going to the Vatican, Milan, and Turin. The monastery was suppressed in 1803 by the French, but its 15th- to 17th-century buildings survive, including the tomb of the saint, whose relics are preserved in the museum. During the medieval period the town was ruled by the Lombard kings and Frankish emperors. The bishopric was created in 1014. In 1176 the town fought against Emperor Frederick I Barbarossa at the Battle of Legnano, which ended his attempted invasion of northern Italy. In 1748 Bobbio became part of Savoy. Besides the abbey of S. Colombano, notable landmarks include the Romanesque and Baroque cathedral, the medieval Ponte Vecchio (Old Bridge) over the Trebbia, the 15th-century Casa di Teodolinda, the 14th-century Palazzo Malaspina, and the 17th-century church of Sta. Maria dell’Aiuto.
Bobbio is a commercial and tourist centre on a busy road between the Emilia plain and Genoa. Pop. (2006 est.) mun., 3,732.