In the region between the rivers Lech and Enns, the wandering Baiuvarii were converted to Christianity in the seventh century, while the Avari, to the east, remained pagan.

[13] But in May 864,[14] Pope Nicholas I, writing to King Louis, noted that Bishop Hartwig of Passau had been paralysed for the previous four years (abhinc quattuor annos), but that he could not simply be deposed or set aside; he could, however, resign the diocese, if he were able to execute the proper documents.

[21] In July 900, Archbishop Dietmar of Salzburg, Bishops Waldo of Frising, Erchanbald of Eichstatt, Zacharias of Säben-Brixen, Tuto of Ratisbon, and Richarius of Passau, sent a letter of complaint to Pope John IX.

[27] When, after the victory the Battle of Lechfeld, the Germans pressed forward and regained the old Ostmark, Bishop Adalbert (946-971) hoped to extend his spiritual jurisdiction over Hungary.

[29] His successor, Christian (991-1002) received in 999 from Emperor Otto III the market privilege and the rights of coinage, taxation, and higher and lower jurisdiction.

[30] Bishop Christian attended the diet of Frankfurt in 1007, at which the decision was taken to establish the diocese of Bamberg, and in 1012 he participated in the consecration of its new cathedral.

During his time the cathedral chapter made its appearance, but there is little information concerning its beginning as a distinct corporation with the right of electing a bishop.

[32] In 1175, he held a council in Passau, in which he had Pope Gregory's synodical letters of 1074 and 1075 read to the assembly; they mandated clerical celibacy.

There was difficulty in enforcing the mandate, and Altmann wrote to the pope, who replied that if one of the clergy complied, he could be restored to his position, but if one refused, he was to be cut off completely.

Bishop Conrad attended the diet of Ratisbon on 17 September 1156, and witnessed the privilegium of the Emperor Frederick Barbarossa, in which he elevated the Ostmark of Austria into a duchy.

[39] Bishop Diepold of Berg went on the Third Crusade with Frederick Barbarossa in 1189, accompanied by the dean of the cathedral, Tageno,[40] whose diary contributed to later authors.

He took stringent measures against the relaxed monasteries, introduced the Franciscans and Dominicans into his diocese, promoted the arts and sciences, and collected the old documents which had survived the storms of the preceding period, so that to him we owe almost all our knowledge of the early history of Passau.

[43] Bishop Peter, formerly Canon of Breslau, contributed to the House of Habsburg by bestowing episcopal fiefs on the sons of King Rudolph.

Cardinal Guido di Borgogna (Guy de Bourgogne), as papal legate, held a council in Vienna on 10 May 1267, attended, among many others, by Bishop Peter of Passau.

[48] In fact, in April 1313, Pope Clement had granted Henri a license for seven years to study civil law, with the provision that he reside in one of his benefices.

[50] Finally, Pope John XXII appointed Albert of Saxony to the diocese of Passau, on 14 June 1320, though he was only in minor orders, and rector of the parish of Vienna.

At the request of the archbishop of Salzburg, Pope Martin V issued a papal bull on 6 August 1418, "intenta Semper", in which he cancelled the arrangements made by John XXIII with respect to Passau.

Towards the close of the fifteenth century the conflict between an Austrian candidate for the see and a Bavarian brought about a state of war in the diocese.

[60] Bishop Ulrich died on 2 September 1479, and in October, claiming that they had received no notice of the Emperor's candidate, they proceeded to their usual and customary election.

[63] The emperor's nominee was George Hasler, who had studied at the University of Vienna and been a follower of the Franciscan inquisitor, John of Capistrano.

[75] The last Bavarian prince-bishop was Urban, who in his struggles during the Reformation received substantial aid for the Austrian part of the diocese from Albert V, Duke of Bavaria, and, after 1576, from Emperor Rudolf II.

[76] His nephew and successor, Bishop Joseph Dominicus von Lamberg (1723–1762), was appointed a cardinal by Pope Clement XII on 20 December 1737.

In November 1719, the Emperor Charles VI wrote to Pope Clement XI, requesting that he elevate the bishopric of Vienna to the rank of metropolitan see.

[78] When Vienna was raised to an archdiocese in 1722, Bishop Raymond von Rabatta relinquished the parishes beyond the Viennese Forest, but in compensation the diocese of Passau was exempted from the metropolitan authority of Salzburg, and became a metropolitan diocese itself, directly dependent upon the Holy See (Papacy); the bishop obtained the pallium for himself and his successors.

[79] Archbishop Leopold Ernst von Firmian (1763–1783), created cardinal by Pope Clement XIV on 14 December 1772,[80] established an institute of theology at Passau, and, after the suppression of the Jesuits in 1773,[81] founded a lyceum.

A concordat between Bavaria and the Papacy was negotiated by Cardinal Ercole Consalvi and Baron Johann Casimir Häffelin, and signed on 5 June 1817.

[87] Article IX granted the kings of Bavaria in perpetuity the right to nominate candidates to all the vacant archbishoprics and bishoprics in the kingdom, subject to papal approval.

[88] On 1 April 1818, Pope Pius VII issued the bull "Dei ac Domini", in which he put into effect canonically the changes agreed to in the Concordat with Bavaria.

[93] Passau was made directly subject to the Holy See until the death of the last prince-archbishop, Leopold von Thun, which took place on 22 October 1826.

[94] Pope Benedict XVI was born and baptized on Holy Saturday, 16 April 1927, at Marktl am Inn, which is located within the Diocese of Passau.