The Electorate of Mainz, also known in English by its French name, Mayence, is the most prestigious and among the most influential states of the Holy Roman Empire from its creation to the dissolution of the HRE in the early years of the 19th century.

In the Roman Catholic hierarchy, the Archbishop-Elector of Mainz is the Primate of Germany (primas Germaniae), a purely honorary dignity that is unsuccessfully claimed from time to time by other Archbishops.

There are only two other ecclesiastical Prince-electors in the Empire: the Electorate of Cologne and the Electorate of Trier.The Archbishop-Elector of Mainz is also archchancellor of the Holy Roman Empire and, as such, ranks first among all ecclesiastical and secular princes of the Empire, and is second only to the Emperor.

His political role, particularly as an intermediary between the Estates of the Empire and the Emperor, was considerable.