Kniaz’ or knyaz (князь in Russian and Ukrainian; 'knez' in Serbian; cneaz in Romanian fem. kniahynia, княгиня) is a title originated in the history of some Slavic lands (Ukraine, Ruthenia, Russia, Serbia, Bulgaria). It is usually translated into English either as Prince or Duke, although the correspondence is not exact. The etymology is probably related to the English King and the German König via Scandinavian konung. It is also possible that it is an even earlier borrowing from the Proto-Germanic *Kuningaz, a form also borrowed by Finnish (Kuningas). The meaning was changing during history.

Initially it was used to denote the chieftain of a tribe. Later, with the development of feudal statehood it become the title of a ruler of a state (княжество, kniazhestvo, translated as duchy or principality), i.e. of Kievan Rus'. In such cases the title is better translated as Prince.

As the degree of centralization grew, the ruler acquired the title Velikii Kniaz (translated as Grand duke, see Russian Grand Dukes). He ruled a Velikoe Knyazhestvo (Grand Duchy), while a ruler of its vassal constituent (udel, udelnoe kniazhestvo) was called udelny kniaz or simply kniaz.

When Kievan Rus' became fragmented in the 13th century, the title Kniaz continued to be used in Ruthenian states, including Novgorod, Vladimir-Suzdal' (later Muscovy), Halych-Volynia, and in the Grand Duchy of Lithuania.

As Muscovy gained dominion over much of former Kievan Rus', Velikii Kniaz Ivan IV of Russia in 1547 was crowned as Tsar, and tsars become Emperors. The title Velikii Kniaz has been applied to sons and grandsons (through male lines) of the Tsars and Emperors of Russia, see Titles for Tsar's family.

Gradually, Kniaz has become a hereditary title of nobility granted by Tsar. The title kniaz (in this case it corresponds to Duke) usually came with udel (land, property), i.e., the term Duchy will be a close match. Unusually many of "kniazes" were in the lands of Caucasus.

Finally, within the Russian Empire of 1809-1917, Finland was called Grand Duchy of Finland (Velikoe Kniazhestvo Finlandskoe).

Related articles

• History of Russia
• Rulers of Kievan Rus
• Tsars