COMACCHIO, Diocese of. – An episcopal see of Emilia, in the province of Ferrara, suffragan of Ravenna. Its origins have often been traced back to the 6th century, with the first titular of the see being Bishop Pacaziano (502), who in fact belongs to Imola. Likewise, another anonymous bishop of 592 stems from a spurious diploma of Gregory the Great to Mariniano, bishop of Ravenna (Jaffé-Wattenbach, 1883 a.).
The first historically attested bishop of Comacchio is Vincenzo, who lived in the 8th century, as attested by an inscription found in the cathedral of Comacchio, which describes him as a contemporary of Archbishop Felix of Ravenna (708–724). Later, mention is made of Vitale in a diploma of Charlemagne dated 787; of Cipriano, who in 858 subscribed to a charter in favour of the monastery of Palazziola; and of Stefano, appointed by John VIII and mentioned in two diplomas of the same pope to Count Berengar. As suffragan of Ravenna, the bishops of Comacchio often took part in the synods of the metropolitan see; for example, Orso (954), Giorgio (997), succeeded by Giovanni, of whom St Peter Damian speaks and who died as a penitent in the monastery of Pomposa. Comacchio took part in the Guibertist schism (Clement III) under Bishop Adalberto, who dated his acts according to the antipope. Likewise, during the Western Schism, Comacchio became a field of contention among the rival popes.
The situation was normalized with the elevation of Martin V to the papal throne. The duchy of Comacchio was first disposed of by the popes; in the 10th century it was held by the Empress Adelaide, after whose death Gregory V entrusted it to the archbishop of Ravenna, Gerbert. In more recent times it was the subject of long disputes between the Holy See and Austria, and in the 18th century much ink was spilled over the rights of the Church and the Empire to the duchy.
Among the ancient abbeys in the territory of Comacchio that exercised notable influence on medieval Italian religious life are to be mentioned: Santa Maria in Aula Regia (Benedictine), already flourishing in the 10th century, later falling into decay and restored in the 15th by Bishop Mainardino; San Giacomo de Cella Volana and, especially, the abbey of Pomposa (q.v.), existing in 874 but of much earlier origin, often the object of imperial and royal privileges.
It produced notable figures such as Peter Damian and the musician Guido d’Arezzo. Having declined, partly because of the unhealthy climate, it was later subjected to secular domination under Alexander VI and Innocent VIII.
The cathedral of Comacchio, dedicated to St Cassian, was rebuilt by Bishop Sigismondo Isei in 1659 and completed by his successor Nicolò Arcani.
The diocese, covering an area of 1,600 km², comprises 27 parishes, with a population of 73,000 Catholics, 27 diocesan priests, and 10 regular clergy (1948).