The original seat of the bishopric lay in the eastern part of Carinthia in the valley of the
Lavant River. It was here, in the parish of
Sankt Andrä, that Archbishop Eberhard II of Salzburg established a
collegiate chapter with the consent of
Pope Innocent III and Holy Roman Emperor
Frederick II on 20 August 1212. Its regular canons followed the
Rule of St. Augustine; its members were chosen from the cathedral chapter of Salzburg. In about the year 1223, the Archbishop of Salzburg asked
Pope Honorius III to allow him to found a bishopric at Sankt Andrä on account of its great remoteness and the difficulty of travelling there. After the pope had had the archbishop's request examined by commissioners and gave his consent, Eberhard drew up the deed of foundation on 10 May 1228, wherein he secured possession of the episcopal chair for himself and his successors in perpetuity. He named as first suffragan bishop his court chaplain
Ulrich (died 1257), who had previously been priest of
Haus im Ennstal in the
Duchy of Styria.
St. Andrew's Church in Sankt Andrä became the diocese's cathedral. In the deed of foundation of the new bishopric, no exact boundaries were defined. In a deed of Archbishop Frederick II of Salzburg of 1280, seventeen parishes, situated partly in Carinthia and partly in
Styria, were described as belonging to Lavant; the extent of the diocese was rather small, but the bishops also attended to the office of
vicar-general (diocesan deputy) of the Archbishops of Salzburg for some scattered districts; they also frequently attended to the office of
Vicedominus (bishop's feudal deputy in secular affairs) at
Friesach. The tenth bishop, Dietrich von Wolfsau (served 1318–1332), is mentioned in deeds as the first (honorific) prince-bishop; he was also secretary of the
Habsburg duke
Frederick the Handsome, and was present at the
Battle of Mühldorf in 1322. Since the twenty-second bishop, Theobald Schweinbeck (served 1446–1463), the bishops bore the title of
Fürst (prince). The following prominent bishops deserve special mention: the humanist
Johann I von Rott (served 1468–1482), who later became
Prince-Bishop of Breslau; Georg II Agrikola (served 1570–1584), who after 1572 was simultaneously
Bishop of Seckau; Georg III Stobäus von Palmburg (served 1584–1618), a significant promotor of the
Counter-Reformation; and Maximilian Gandolph Freiherr von Kienburg (served 1654–1665), who did much towards increasing the financial resources of the diocese. By new regulations under Holy Roman Emperor
Joseph II, several territories were added to the Diocese of Lavant. Prince-Archbishop Michael Brigido of
Laibach ceded a number of parishes to the Diocese of Lavant in 1788. The extent of the diocese was changed by the circumscription of 1 June 1859. The valley of the Lavant and the
district of Völkermarkt in Carinthia were given to the
Diocese of Gurk; in consequence, the District of Marburg was transferred from Seckau to Lavant; leaving Lavant comprising the whole of southern
Styria. By the decree of the
Congregation of the Consistory of 20 May 1857, the see of the bishop was moved from Sankt Andrä to Marburg and the
parish church,
a church of St. John the Baptist, was elevated into a cathedral. On 4 September 1859, Bishop
Anton Martin Slomšek (served 1846–1862) formally entered Marburg. In 1962, the diocese was renamed to the
Diocese of Maribor. == List of bishops ==