The diocese was founded in 739. The bishops were Princes of the Holy Roman Empire, ruling a territory known as the Prince-Bishopric of Regensburg. They were not among the most powerful Prince-Bishops, due to the existence of other reichsfrei authorities in Regensburg[3] that prevented them from consolidating a major territorial base.
^Regiomontanus was named bishop of Regensburg (or at least promised the title) shortly before his death on 6 July 1476 as part of the rewards promised to him by Sixtus IV.
Rudolf Schmidt, Regiomontanus, Johann in: Deutsche Buchhändler. Deutsche Buchdrucker vol. 5 (1908), 797f.
Reported by Paul Jovius (Giovio; 1483-1552), Ab hac commendatione eruditi nominis creatus est a Xysto Quarto Ratisponensis Episcopus (cited by Pierre Gassendi).
Hagen, J. (1911) in The Catholic Encyclopedia (s.v. Johann Müller) opines that the report by Jovius "is not improbable, since by this dignitary title the pope could give more force to his invitation. Yet it seems certain that Müller never occupied the episcopal chair."