Archbishopric of Mainz

This archbishopric was a substantial ecclesiastical principality of the Holy Roman Empire. It included lands near Mainz on the both the Left and Right Banks of the Rhine, as well as territory along the Main above Frankfurt (including the district of Aschaffenburg), and territory around Erfurt in Thuringia. The Archbishop was also, traditionally, one of the Imperial Prince-Electors, the Archchancellor of Germany, and presiding officer of the electoral college.

In 1802, Mainz lost its archiepiscopal character. In the secularizations that accompanied the Reichsdeputationshauptschluss 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 Erfurt to Prussia. Dalberg retained the Aschaffenberg 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. Since then the Diocese of Mainz has had two cardinals and via various concordats was allowed to retain the medieval tradition of the cathedral chapter electing a successor to the bishop. This practice has all but disappeared in the Roman Catholic Church.
Another specialty: Aside from Rome, the See of Mainz is the only other see referred to as a "Holy See", although this usage became rather less common.

Archbishops of Mainz, 745-1802