King in Prussia
King of the Prussian state
King in Prussia (German: König in Preußen) was a title used by the Prussian kings (also in personal union Electors of Brandenburg) from 1701 to 1772. Subsequently, they used the title King of Prussia (König von Preußen).
The House of Hohenzollern ruled Brandenburg as Prince-Electors, and were subjects of the Holy Roman Emperor. Since 1618, the Electors of Brandenburg had also ruled the Duchy of Prussia, which lay outside the empire, in a personal union. The dual state was known unofficially as Brandenburg-Prussia. Originally the dukes of Prussia held the fief as vassals of the King of Poland, until the Treaties of Labiau (1656) and Bromberg (1657), with which Frederick William, the Great Elector, achieved full sovereignty from the Polish Crown. His son, Elector Frederick III, then sought to show his greatness by adopting the title king.
At the time, the only royal titles within the Holy Roman Empire were those of King of the Romans (held by the Holy Roman Emperor or his heir apparent) and King of Bohemia (held more or less continuously since the 16th century by the Holy Roman Emperors in a de facto personal union). However, Prussia lay outside the empire, and the Hohenzollerns were fully sovereign over it. Frederick thus argued that German law of the time allowed him to rule Prussia as a kingdom, outside the borders of the Holy Roman Empire.
“King in Prussia” enters the record as king of the Prussian state. Crown Archives preserves that source wording while asking what King, Prussia and Prussian can confirm, complicate or overturn.
Why this record matters
“King in Prussia” is worth following because a concise public description often conceals a longer documentary argument. Here, King, Prussia and Prussian provides the most credible route into that argument.
Biographical claims are most persuasive when dates, appointments and relationships can be traced to records created close to the events described. The source revision retrieved here is dated Feb 24, 2026. The linked authority identifier is Q3240735. None of the 1 selected statements returned an explicit reference. The first chronological checks are 1701, 1772, 1618 and 1656.
Later biographies can compress uncertainty and repeat inherited reputations, so apparently settled claims may still require comparison. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “King in Prussia” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.