Diocese in the Province of Turin, Piedmont, Northern Italy. The city is situated at an elevation of about 1600 feet above sea-level, in a wide valley to the right of the Dora Riparia; near by are some valuable marble quarries ( verde di Susa). The cathedral, dedicated to St. Justus and founded by Ulderico Manfredi, (1029) contains much of interest: specimens of very fine inlaid work in the choir stalls; the baptismal font and the bronze group of the "Madonna del Roccia Melone" (Madonna with the Child, St. George transfixing the dragon, and a knight on bended knee); in a chapel may be seen the tomb of the Countess Adelaide with her statue in wood, an excellent example of eleventh-century work, In ancient times the city was called Segusio, and in the days of Augustus it still had a king, who held sway over fourteen other towns. This king submitted voluntarily to the Romans and erected, in honour of Augustus, a triumphal arch, which still exists. Under Nero the kingdom was abolished and became a municipium. In addition to the arch, there still exist the ruins of the Thermæ Gratianæ constructed by Valentinian I. Susa being situated near one of the principal Alpine valleys was always a place of great strategic importance. Constantine destroyed it while advancing against Maxentius; after the Langobard invasion, the Byzantine garrison remained there till 593. Later it came into possession of the Franks. It was captured twice by Pepin and once by Charlemagne (774), who by a skilful manœuvre compelled the Lombards to fall back on Pavia. From that time it formed part of the Kingdom of Italy. In 942 it became the residence of Ardoino Glabrio, Count of Susa and later Marquis of Turin, who was succeeded by Manfredo (975), Olderico (1001), and Adelaide (1034). The latter having married Odo of Savoy in her third marriage, Susa passed into the power of Savoy. In the twelfth century it acquired communal liberty; though destroyed (1174) by Barbarossa, it soon rose again, and in 1197 had already adopted new statutes. In the wars of the thirteenth century it sided with the Guelphs, and was a subject of dispute between the marquises of Saluzzo and the counts of Savoy; it was definitely given to the latter in 1295. Later during the wars of the sixteenth and eighteenth centuries it fell on five occasions into the hands of the French (1536-62; 1628-31; 1639-42; 1704-7; 1798-1814); in 1798 the fortifications constructed by the dukes of Savoy were dismantled.

In early days, Susa seems to have belonged to the Diocese of Maurienne. The Abbey of St. Justus having been erected in 1029, the abbot had quasi-episcopal jurisdiction. The Benedictines succeeded the Canons Regular, and under Benedict XIV were replaced by secular canons. In 1772 this prelacy nullius became a diocese, and the territory of the famous Abbey of Novalesa was added to that of Susa. The first bishop was Francesco M. Ferraris. Napoleon suppressed the see in 1803, but it was restored in 1817, and its territory increased by the inclusion of the Abbey S. Michele della Chiusa. The diocese, suffragan of Turin, contains 61 parishes with 75,000 inhabitants, and 130 secular and regular priests; 5 religious houses of men and 7 of women; 3 institutes for boys and 3 for girls.

CAPPELLETTI, Le Chiese d'Italia; SACHETTI, Memorie della Chiesa di Susa (Turin, 1786); GENUI, Il marchesato di Susa (1891); BACCO, Cenni storici su Avigliana e Susa (Susa, 1881).

U. BENIGNI