Prince-elector
Prince-electors (German: Kurfürst) were the group of rulers of German countries which elected the Holy Roman Emperor. In English they were usually called "Electors" and included the Elector of Brandenburg, who also began ruling as King of Prussia, and the Electors of Hanover, who were also kings of Great Britain after 1714.
Prince-elector Media
The imperial prince-electors left to right: Archbishop of Cologne, Archbishop of Mainz, Archbishop of Trier, Count Palatine, Duke of Saxony, Margrave of Brandenburg and King of Bohemia (Codex Balduini Trevirorum, c. 1340)
Page from an armorial showing the arms of Emperor Frederick III, ca 1415–1493.