Not all incumbents of the Bremian See were
imperially invested princely power as Prince-Archbishops and not all were papally confirmed as bishops. In 1180 part of the Bremian diocesan territory and small parts of the neighbouring
Diocese of Verden were disentangled from the
Duchy of Saxony and became an own territory of
imperial immediacy called
Prince-Archbishopric of Bremen (), a vassal of the
Holy Roman Empire. The prince-archbishopric was an
elective monarchy, with the monarch being the respective archbishop usually elected by the Bremian Chapters at Bremen Cathedral and Hamburg Concathedral, with the latter enfranchised to three capitular votes, and confirmed by the
Holy See, or exceptionally only appointed by the Holy See. Papally confirmed archbishops were then invested by the emperor with the princely
regalia, thus the title
prince-archbishop. However, sometimes the respective incumbent of the see never gained a papal confirmation, but was still invested the princely regalia. Also, the opposite occurred with a papally confirmed archbishop, never invested as prince. A number of incumbents, elected by the chapter, neither achieved papal confirmation nor imperial
investiture, but as a matter of fact nevertheless de facto held the princely power. The respective incumbents of the see bore the following titles: •
Bishop of Bremen from 787 to 845 •
Archbishop of Hamburg and Bishop of Bremen in
personal union (colloquially also Archbishop of Hamburg-Bremen) from 848 to 1072 • Archbishop of Bremen (colloquially also Archbishop of Hamburg-Bremen) from 1072 to 1179 •
Prince-Archbishop of Bremen from 1180 to 1566, paralleled by the de facto rule of Catholic Administrators from 1316 to 1327 and again 1348 to 1360 •
Administrator of the Prince-Archbishopric of Bremen 1316 to 1327, 1348 to 1360, and again 1568 to 1645. Either simply de facto replacing the Prince-Archbishop or lacking canon-law prerequisites, the incumbent of the see would officially only hold the title administrator (but nevertheless colloquially referred to as Prince-Archbishop). Between 1568 and 1645 all administrators were Lutherans, while else they were Roman Catholics. • The last, but only provisional incumbent of the
See, Francis of Wartenberg, therefore bore the title
Vicar Apostolic (1645–1648) == Catholic Bishops of Bremen till 845 ==