The Wittelsbach dynasty which ruled the Duchy of Bavaria was the younger branch of the family which also ruled the Electorate of the Palatinate.
The principality lost its status as an electorate in 1806 with the dissolution of the Holy Roman Empire and became part of the Confederation of the Rhine later that year. During the War of the Fifth Coalition, Austrian troops occupied Regensburg on 20 April 1809; it was shelled and stormed by French troops three days later.
In the Treaty of Paris, Dalberg conceded Regensburg to the Kingdom of Bavaria, which formally incorporated the city on .
Its capital was the city of Regensburg, now in Bavaria, Germany.
The principality also included the Lordships of Donaustauf, Wörth, and Hohenburg, the imperial city of Regensburg, St.
Emmeram's Abbey, and the abbeys Obermünster and Niedermünster.
Dalberg also retained the Principality of Aschaffenburg along the Main river.
Dalberg received the electoral dignity previously accorded to the Electorate of Mainz; his new principality has thus been known in German as ("Electorate of Regensburg").
The principality was created for Karl Theodor von Dalberg, the Elector-Archchancellor of the Empire and the former Archbishop of Mainz, due to the annexation of Mainz itself by the French under the Treaty of Lunéville.
Most of the new principality consisted of the territory of the old Prince-Bishopric of Regensburg, which had been founded in 739 by Saint Boniface.
In return for conceding Regensburg, Dalberg was granted Hanau and Fulda, which he combined with the Principality of Aschaffenburg to create the Grand Duchy of Frankfurt.
Although he had lost the Principality of Regensburg, Dalberg retained the title of Archbishop of Regensburg until his death in 1817, after which time the archbishopric was downgraded to a suffragan diocese of Munich and Freising.
Because the archiepiscopal status of Mainz had also been transferred to the Regensburg diocese, the principality has also been known in English as the Archbishopric of Regensburg.
Because of Bavarian claims on Regensburg, Dalberg was not installed as archbishop until 1 February 1805.