The Principality of Regensburg (German: Fürstentum Regensburg) is a principality within the Holy Roman Empire and the Confederation of the Rhine that exists between 1803 and 1810.

Its capital is the city of Regensburg, now in Bavaria, Germany.

The principality is 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 consistsof the territory of the old Prince-Bishopric of Regensburg, which had been founded in 739 by Saint Boniface.

The principality also includes the Lordships of Donaustauf, Wörth, and Hohenburg, the imperial city of Regensburg, St. Emmeram's Abbey, and the abbeys Obermünster and Niedermünster.

Dalberg also retains the Principality of Aschaffenburg along the Main river.

Dalberg receives the electoral dignity previously accorded to the Electorate of Mainz; his new principality has thus been known in German as Kurfürstentum Regensburg ("Electorate of Regensburg").

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 is not installed as archbishop until February 1, 1805.

The principality loses its status as an electorate in 1806 with the dissolution of the Holy Roman Empire and becomes part of the Confederation of the Rhine later this year.

The Napoleonic Code is introduced in 1809.

During the War of the Fifth Coalition, Austrian troops occupy Regensburg on April 20, 1809; it is shelled and stormed by French troops three days later.

In the Treaty of Paris, Dalberg concedes Regensburg to the Kingdom of Bavaria, which formally incorporates the city on May 22, 1810

In return for conceding Regensburg, Dalberg is granted Hanau and Fulda, which he combines with the Principality of Aschaffenburg to create the Grand Duchy of Frankfurt.

Although he has lost the Principality of Regensburg, Dalberg retains the title of Archbishop of Regensburg until his death in 1817, after which time the archbishopric is downgraded to a suffragan diocese of Munich and Freising.