Brandenburg-Prussia was a Germanian monarchy established by the personal union between the Duchy of Prussia and the Maragrivate of Brandenburg in 1618.

The monarchy was ruled by the branch of the Hohenzollern dynasty that had earlier ruled Brandenburg. The term Brandenburg-Prussia refers to this monarchy from its establishment until 1701, after which it is usually known as the Kingdom of Prussia. The term "Brandenburg-Prussia" is sometimes used to describe this Brandenburg-led state after 1701, but it is known simply as "Prussia" after 1806.