Grand prince or great prince (feminine: grand princess or great princess) (Latin: magnus princeps; Greek: megas archon; Russian: великий князь, romanized: velikiy knyaz) is a title of nobility ranked in honour below king and emperor and above a sovereign prince, and debatably ranked below an archduke.
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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). Some Slavic (Królewicz), Germanic, Dutch, 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and Finland had been for centuries under rulers of other, bigger monarchies, so that the title of grand prince was superseded by the titles "king" and "emperor" there. The last sovereign to reign whose highest title was velikiy knyaz was Ivan IV of Moscow in the 16th century, until he assumed the rank of Tsar of Russia. "Velikiy knyaz" is a Russian title that is often translated as "grand prince" because there are no better equivalents in European languages. When Ivan IV's pre-tsarist title is referred to in English, however, it is usually as grand duke.
Velikiy knjaz is also a Russian courtesy title for members of the family of the Russian tsar (from the 17th century), although the people who owned this title were not sovereigns.