The Wheel of Mainz or Mainzer Rad, in German, was the coat of arms of the Archbishopric of Mainz and thus also of the Electorate of Mainz (Kurmainz), in Rhineland-Palatinate, Germany. It consists of a silver wheel with six spokes on a red background. The wheel can also be found in stonemasons' carvings and similar objects. Currently, the City of Mainz uses a double wheel connected by a silver cross.

The Electorate of Mainz, previously known in English as Mentz and by its French name Mayence, was one of the most prestigious and influential states of the Holy Roman Empire. In the Roman Catholic hierarchy, the Archbishop-Elector of Mainz was also the Primate of Germany, a purely honorary dignity that was unsuccessfully claimed from time to time by other archbishops. There were only two other ecclesiastical Prince-electors in the Empire: the Electorate of Cologne and the Electorate of Trier.