Former patriarchate and metropolitan see on the Natissa River in Friuli (Udine), Italy. Having been founded
as a Roman military colony c. 180 b.c., Aquileia was greatly prized by the Caesars as a port and bastion against the Illyrians. A 5th-century legend traces its Christianity to St. Mark and names St. Hermagoras its first bishop, though its beginnings were in the mid-3d century. In the 5th century it exercised metropolitan rights over Venice, Istria, West Illyricum, Rhaetia, and Noricum; and its bishops claimed the title of patriarch in the mid-6th century (Pelagius I, Epist. ). When the Huns destroyed Sirmium in 452, they besieged Aquileia, which thereafter extended its jurisdictional claims to the Pannonian borderlands.
After the condemnation of the three chapters in 553 by the Council of constantinople ii and Pope vigilius, Patriarch Paulinus I rejected the condemnation in a provincial council (554); the schism thus created lasted until 607, when Bishop Candidianus restored communion. However, Paulinus had fled to the isle of Grado in Byzantine territory before the Lombards in 568; hence the Lombards elected their own patriarch for ancient Aquileia with its see at Cividale, and this territory remained in schism until Patriarch Peter, with the consent of King Cunibert, made peace with Rome in a synod at Pavia (c. 700).
In 716 two dioceses were recognized: Aquileia and Grado. Grado's line of patriarchs continued until the 15th century. Under Paulinus II (c. 785–804), a friend of charlemagne, missioners were sent among the Avars and Slovenes, and the Drava River was made the boundary between Aquileia and the See of Salzburg in 811. Patriarch Maxentius attempted vainly to reunite Aquileia with Grado in a synod at Mantua (827), when the patriarch ate was granted immunity and free election.
The present cathedral was begun by Poppo (1019–42), and in 1077 Henry IV granted suzerainty to Patriarch Sigehard (1068–77) as Count of Friuli and Istria. Berthold of Andechs changed the see to Udine in 1238, and Gregory of Montelongo (1251–69) was the first Italian to become patriarch. Beset by its neighbors, particularly Venice, the patriarch ate functioned only partially; but Marquard of Randech (1365–81) issued a civil and penal code (Constitutiones patriae Foriiulii ) with the consent of the city's parliament. Louis of Tech (1412–39) joined the king of Hungary in war against Venice, and the territory was then taken over by the Venetians. When the Hapsburgs assumed jurisdiction over Aquileia, the patriarch ate was absorbed by Venice; leaders such as Marco Barbo (1465–91), Ermolao Barbaro (1491–93), Giovanni and Daniello Delfino (1658–99, 1734–51) subsequently ruled as patriarchs.
Under Austrian pressure, benedict xiv suppressed the Patriarch ate of Aquileia (July 6, 1751) and erected the archbishoprics of Udine and Gorizia, and the former patriarch ate was made a parish church depending immediately on the Holy See.
Archeological excavations have uncovered an imperial villa under the foundations of the ancient church, which after the peace of Constantine was enlarged and decorated with mosaics of the Good Shepherd, Jonas, etc. A stone pavement (lithostratos) was uncovered. The baptistery was on one side and surrounded an octagonal basin. In the 5th century a large basilica with three naves and a decorated pavement was destroyed by fire. New constructions were made under justinian i and at that time a polygonal baptistery was added. The present campanile tower dates from the patriarch ate of Poppo.
Bibliography: p. paschini, Storia del Friuli, 3 v. (Udine 1934–36). g. brusin, Aquileia e Grado (2d ed. Padua 1952). m. m. roberti, g. bovini, g. cuscito, eds., Aquileia e l'alto Adriatico Vol. 2: Aquileia e l'Istria (Udine 1972). s. tavano, j. lemariÉ, m. m. roberti, Aquileia e l'alto Adriatico Vol. 1: Aquileia e Grado (Udine 1972). y.-m. duval, e. cattaneo, j. lemariÉ, eds., Aquileia e Milano (Udine 1973). g. c. menis, e. jastrzebowska, g. rinaldi, eds., Mosaici in Aquileia e nell'alto Adriatico (Udine 1975). j. nordhagen, g. cuscito, j. lemariÉ, eds., Aquileia e Ravenna (Udine 1978). c. jÄggi, "Aspekte der städtebaulichen Entwicklung Aquileias in frühchristlicher Zeit," Jahrbuch für Antike und Christentum, Jahrgang 33 1990 (Münster 1991) 158–196. g. cuscito, "Alle origini della storiografia critica sul primo cristianesimo aquileiese," Quaeritur inventus colitur (Vatican City 1989) 161–175. g. c. wataghin, "Problemi e ipotesi sulla basilica della Beligna di Aquileia," Quaeritur inventus colitur (Vatican City 1989) 71–90.
[f. x. murphy/eds.]