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The title grand prince or great prince (Latin: magnus princeps, Greek: megas archon) ranked in honour below king and emperor and above a sovereign prince.

Grand duke is the usual and established, though not literal, translation of these terms in English and Romance languages, which do not normally use separate words for a "prince" who reigns as a monarch (e.g., Albert II, Prince of Monaco) and a "prince" who does not reign, but belongs to a monarch's family (e.g., Prince William, Duke of Cambridge). German, Dutch, Slavic and Scandinavian languages do use separate words to express this concept, and in those languages grand prince is understood as a distinct title (for a cadet of a dynasty) from grand duke (hereditary ruler ranking below a king).

The title of grand prince was once used for the sovereign of a "grand principality". The last titular grand principalities vanished in 1917 and 1918, the territories being united into other monarchies or becoming republics. Already at that stage, the grand principalities of Lithuania, Transylvania and Finland had been for centuries under rulers of other, bigger monarchies, so that the title of grand prince was superseded by a royal title (king/tsar) or an imperial one (emperor). The last sovereign to reign whose highest title was grand prince was Ivan IV of Moscow in the 16th century, until he assumed the rank of Tsar of Russia. When Ivan IV's pre-tsarist title is referred to in English, however, it is usually as grand duke.

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