The County Palatine of the Rhine (later the Electoral Palatinate (German: Kurpfalz), was a historical territory of the Holy Roman Empire, originally a palatinate administered by a count palatine. Its rulers served as prince-electors (Kurfürsten) from "time immemorial", were noted as such in a papal letter of 1261, and were confirmed as electors by the Golden Bull of 1356.
The fragmented territory stretched from the left bank of the Upper Rhine, from the Hunsrück mountain range in what is today the Palatinate region in the German federal state of Rhineland-Palatinate and the adjacent parts of the French region of Alsace (bailiwick of Seltz from 1418 to 1766) to the opposite territory on the east bank of the Rhine in present-day Hesse and Baden-Württemberg up to the Odenwald range and the southern Kraichgau region, containing the capital cities of Heidelberg and Mannheim.
The Counts Palatine of the Rhine held the office of Imperial vicars in the territories under Frankish law (in Franconia, Swabia and the Rhineland) and ranked among the most significant secular Princes of the Holy Roman Empire. Their climax and decline is marked by the rule of Elector Palatine Frederick V, whose coronation as King of Bohemia in 1619 sparked the Thirty Years' War. After the 1648 Peace of Westphalia, the ravaged lands were further afflicted by the "Reunion" campaigns launched by King Louis XIV of France, culminating in the Nine Years' War (1688–97). Ruled in personal union with the Electorate of Bavaria from 1777, the Electoral Palatinate was finally disestablished with the German mediatization in 1803.