The Diocese of Mainz was governed by bishops until 745 when it was elevated in rank to an archbishopric. By the 10th century, the archbishops had secular jurisdiction over a territory of the Holy Roman Empire. This was the future Electorate of Mainz. From the 13th century, the archbishops were first in precedence among the prince-electors of the empire and ex officio archchancellor. Their secular and spiritual jurisdictions, however, did not coincide geographically.

In church hierarchy, the archbishop of Mainz was the primas Germaniae.

Bishops and archbishops Legendary bishops before 350

Crescens c. 80–103 Marinus c. 103–109 St. Crescentius c. 109–127 Cyriacus c. 127–141 Hilarius c. 141–161 Martin I c. 161–175 Celsus c. 175–197 Lucius c. 197–207 Gotthard c. 207–222 Sophron c. 222–230 Heriger I c. 230–234 Ruther c. 234–254 Avitus c. 254–276 Ignatius c. 276–289 Dionysius c. 289–309 Ruprecht I c. 309–321 Adalhard c. 320s Lucius Annaeus c. 330s

Bishops, –745

Martin II – c. 360s Sidonius I c. late 360s – c. 386 Sigismund c. 386 – c. 392 Theonistus or Thaumastus"Theomastus (or Thaumastus) was bishop of Mainz in the early fifth century."(Gregory of Tours, Glory of the Confessors: Glory of the Confessors. Translated by Raymond Van Dam (Liverpool University Press, 1988), 40n). This figure is mentioned by Gregory of Tours: “Theomastus was noted for his holiness in accordance with the meaning of his name, and he is said to have been bishop of Mainz. For some unknown reason, he was expelled from Mainz and went to Poitiers. There he ended his present life by remaining in a pure confession.”(Gregory of Tours, Glory of the Confessors: Glory of the Confessors. Translated by Raymond Van Dam (Liverpool University Press, 1988), 39). Maximus Lupold c. 392 – c. 409 Nicetas c. 409 – c. 417 Marianus c. 417 – c. 427 Aureus c. 427 – c. 443 Eutropius c. 443 – c. 467 Adalbald Nather Adalbert (I) Lantfried Sidonius II ? – c. 589 Siegbert I c. 589–610 Ludegast c. 610–615 Rudwald c. 615 Lubald ? fl. c. 625 Rigibert 708-724 Gerold 724–743 Gewilip c. 744 – c. 745

Archbishops, 745–1251

Saint Boniface 745–754At this time, Mainz did not have the status of an archdiocese. Bonifacius had been titular archbishop Lullus 754–786 (First archbishop) Richholf 787–813 813–826 Odgar 826–847 Rabanus Maurus 848–856 Karl 856–863 Ludbert 863–889 Sunderhold 889–891 Hatto I 891–913 Herigar 913–927 Hildebert 927-937 Frederick 937–954 William 954–968 Hatto II 968–970 Rudbrecht 970–975 Willigis 975–1011 Erkanbald 1011–1021 Aribo 1021–1031 Bardo 1031–1051 Luitpold 1051–1059 Siegfried I 1060–1084 Wezilo 1084–1088 Rudhart 1088–1109 Adalbert I von Saarbrücken 1111–1137 1138–1141 Markholf 1141–1142 Henry I 1142–1153 Arnold von Selenhofen 1153–1160 Christian I 1160–1161 Rudolf of Zähringen 1160–1161 (opposing) Conrad I of Wittelsbach 1161–1165 Christian I 1165–1183 Conrad I of Wittelsbach (restored) 1183–1200 Luitpold von Scheinfeld 1200–1208 Sigfried II von Eppstein 1200–1230 (in opposition until 1208) Sigfried III von Eppstein 1230–1249 Christian II von Weisenau 1249–1251

Archbishops and Prince-Electors, 1251–1803

Gerhard I von Daun-Kirberg 1251–1259 Werner II von Eppstein 1260–1284 Heinrich II von Isny 1286–1288 Gerhard II von Eppstein 1286–1305 Peter of Aspelt 1306–1320 Matthias von Bucheck 1321–1328 Heinrich III von Virneberg 1328–1337 Baldwin of Luxembourg 1328–1336, administrator Gerlach von Nassau 1346–1371 Johann I von Luxemburg-Ligny 1371–1373 Louis of Meissen 1374–1379 Adolf I von Nassau 1379–1390 Konrad II von Weinsberg 1390–1396 Joffrid von Leiningen 1396–1397 Johann II von Nassau 1397–1419 Conrad III of Dhaun, Wild- and Rhinegrave zum Stein 1419–1434 Dietrich Schenk von Erbach 1434–1459 Dieter von Isenburg 1459–1461 Adolf II von Nassau (or Adolf III) 1461–1475 Dieter von Isenburg (restored) 1476–1482 Adalbert III of Saxony 1482–1484 Bertold von Henneberg-Römhild 1484–1504 Jakob von Liebenstein 1504-1508 Uriel von Gemmingen 1508–1514 Albert III of Brandenburg 1514–1545 Sebastian von Heusenstamm 1545–1555 Daniel Brendel von Homburg 1555–1582 Wolfgang von Dalberg 1582–1601 Johann Adam von Bicken 1601–1604 Johann Schweikhard von Kronberg 1604–1626 Georg Friedrich von Greiffenklau 1626–1629 Anselm Casimir Wambold von Umstadt 1629–1647 Johann Philipp von Schönborn 1647–1673 Lothar Friedrich von Metternich-Burscheid 1673–1675 Damian Hartard von der Leyen-Hohengeroldseck 1675–1678 Karl Heinrich von Metternich-Winneburg 1679 Anselm Franz von Ingelheim 1679–1695 Lothar Franz von Schönborn 1695–1729 Franz Ludwig von Pfalz-Neuburg 1729–1732 Philipp Karl von Eltz-Kempenich 1732–1743 Johann Friedrich Karl von Ostein 1743–1763 Emmerich Joseph von Breidbach zu Bürresheim 1763–1774 Friedrich Karl Joseph von Erthal 1774–1802 Karl Theodor von Dalberg 1802–1803Karl Theodor von Dalberg died in 1817 and was Archbishop of Regensburg 1803–1810, Prince of Frankfurt 1806–1810 and Grand Duke of Frankfurt 1810–1813.

Bishops, 1802–present Joseph Ludwig Colmar (1802–1818) Joseph Vitus Burg (1829–1833) Johann Jakob Humann (1833–1834) Petrus Leopold Kaiser (1834–1848) Wilhelm Emmanuel Freiherr von Ketteler (1850–1877) sede vacante (1877–1886) Paul Leopold Haffner (1886–1899) Heinrich Brück (1900–1903) Georg Heinrich Kirstein (1903–1921) Ludwig Maria Hugo (1921–1935) Albert Stohr (1935–1961) Hermann Cardinal Volk (1962–1982) Karl Cardinal Lehmann (1983–2016) Peter Kohlgraf (2017– ...)

Auxiliary bishops Before 1807

Since 1954 Joseph Maria Reuß (Reuss) (1954–1978) Wolfgang Rolly (1972–2003) Franziskus Eisenbach (1988–2002) Werner Guballa (2003–2012) Ulrich Neymeyr (2003–2014) Udo Markus Bentz (2015– 2024) Joshy George Pottackal OCarm (2026-)

Electoral title The Elector of Mainz was one of the seven Prince-electors of the Holy Roman Empire. As both the Archbishop of Mainz and the ruling prince of the Electorate of Mainz, the Elector of Mainz held a powerful position during the Middle Ages. The Archbishop-Elector was president of the electoral college, archchancellor of the empire, and the Primate of Germany as the papal legate north of the Alps, until the dissolution of the empire in 1806.

This archbishopric was a substantial ecclesiastical principality of the Holy Roman Empire. Its area reached 3200 sq. miles by the end of the Empire. The last elector was Karl Theodor von Dalberg, who lost his temporal power when the archbishopric was secularized in 1803. The ecclesiastical principality included lands near Mainz on both the left and right banks of the Rhine, as well as territory along the Main above Frankfurt (including the district of Aschaffenburg), the Eichsfeld region in Lower Saxony and Thuringia, and the territory around Erfurt in Thuringia. The archbishop was also, traditionally, one of the Imperial Prince-Electors, the Arch-chancellor of Germany, and presiding officer of the electoral college technically from 1251 and permanently from 1263 until 1803.

The see was established in ancient Roman times, in the city of Mainz, which had been a Roman provincial capital called Moguntiacum, but the office really came to prominence upon its elevation to an archdiocese in 780/82. The first bishops before the 4th century have legendary names, beginning with Crescens. The first verifiable Bishop of Mainz was Martinus in 343. The ecclesiastical and secular importance of Mainz dates from the accession of St. Boniface to the see in 747. Boniface was previously an archbishop, but the honor did not immediately devolve upon the see itself until his successor Lullus.

In 1802, Mainz lost its archiepiscopal character. In the secularizations that accompanied the Reichsdeputationshauptschluss ("German mediatization") of 1803, the seat of the elector, Karl Theodor von Dalberg, was moved to Regensburg, and the electorate lost its left bank territories to France, its right bank areas along the Main below Frankfurt to Hesse-Darmstadt and the Nassau princes, and Eichsfeld and Erfurt to Prussia. Dalberg retained the Aschaffenburg area however, and when the Holy Roman Empire finally came to an end in 1806, this became the core of Dalberg's new Grand Duchy of Frankfurt. Dalberg resigned in 1813 and in 1815 the Congress of Vienna divided his territories between the King of Bavaria, the Elector of Hesse, the Grand Duke of Hesse-Darmstadt and the Free City of Frankfurt.

The modern Diocese of Mainz was founded in 1802, within the territory of France and in 1814 its jurisdiction was extended over the territory of Hesse-Darmstadt. Since then it has had two cardinals and via various concordats was allowed to retain the mediæval tradition of the cathedral chapter electing a successor to the bishop.

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