Councils of Aquileia
In the history of Christianity and later of the Roman Catholic Church, there have been several Councils of Aquileia. The Roman city of Aquileia at the head of the Adriatic is the seat of an ancient episcopal see, seat of the Patriarch of Aquileia.
Council of 381 AD 
The council was summoned by the Western Roman Emperor Gratian to address the Arian controversy. It was organized by Ambrose, and presided over by Valerian, Bishop of Aquileia. Thirty-two Western bishops attended.
The Arian Palladius of Ratiaria and Secundianus of Singidunum, were defenders of the Arian position. The Arian position was anathematized by all the bishops other than Palladius, who disputed the legitimacy of the council due to the absence of Eastern bishops.
Council of 553 AD 
The council of 553 inaugurated the Schism of the Three Chapters, that for a century and more separated many churches of northern Italy from the Holy See; in it the Bishops of Venetia, Istria, and Liguria refused to accept the decrees of the Second Council of Constantinople (the 5th General Council, 553 AD), on the plea that by the condemnation of the Three Chapters it had undone the work of the Council of Chalcedon of 451. In Northern Italy the ecclesiastical provinces of Milan and Aquileia broke off communion with the papacy; the former yielding only towards the end of the 6th century, whereas Aquileia protracted its resistance to about 700.
Council of 579 AD 
Council of 698 AD 
Council of 1184 
The Council of 1184 was held against incendiaries and those guilty of sacrilege.
Council of 1409 
In 1409 a council was held by Gregory XII against the pretensions of the rival popes, Benedict XIII (Peter de Luna) and Alexander V (Peter of Candia). He declared them schismatical, but promised to renounce the papacy if they would do the same.
Council of 1596 
In 1596 Francesco Barbaro, Patriarch of Aquileia, held a council at which he renewed in nineteen decrees the legislation of the Council of Trent, including the replacement of the Aquileian Rite with the Tridentine Mass. This was part of a series of synods around the Patriarchate to standardise the Rite with Rome.