The Bishopric of Regensburg (German: Bistum Regensburg) was a small prince-bishopric (Hochstift) of the Holy Roman Empire, located in what is now southern Germany. It was elevated to the Archbishopric of Regensburg in 1803 after the dissolution of the Archbishopric of Mainz, but became a bishopric again in 1817.
The diocese was founded in 739 by Saint Boniface; it was originally subordinate to the archbishop of Salzburg. In the 13th century, the Bishopric of Regensburg became a state of the Holy Roman Empire. By the Reichsdeputationshauptschluss of 1803, the bishopric was united with other territories to form the Archbishopric of Regensburg, with Karl Theodor Anton Maria von Dalberg as archbishop. In 1810, this Principality of Regensburg became part of the Kingdom of Bavaria, although he retained archiepiscopal status. The Bavarian Concordat of 1817 after Dalberg's death downgraded the Archdiocese of Regensburg into a suffragan diocese subordinate to the archbishop of Munich and Freising.