The title of grand duke (Latin, magnus dux; German, Großherzog) was used in Slavic, Baltic and Germanic countries, is ranked in honour below kings but higher than sovereign princes ("Fürst"). The feminine form is grand duchess.
The nation or territory ruled by a grand duke is called a grand duchy.
Grand Duke is the traditional translation of the title, velikii kniaz, which from the 11th century was the title of first the leading Russian prince (in Kiev), then of several Russian princes. From 1328 the velikii kniaz of Muscovy appeared as the Grand Duke for "all of Russia" until Ivan IV in 1547 was crowneded as tsar, thereafter the title was given to sons and grandsons of the tsar and emperors of Russia.
A more accurate translation of the Russian title would be Great Prince - especially in the pre-Petrine era - but the term is neither standard nor widely used in English. In German, however, a Russian Grand Duke was known as a Großfürst, and in Latin as Magnus Princeps.,
This title was not given to consorts of a daughter or granddaughter of a tsar. The daughters and granddaughters of Russian emperors, as well as the consorts of Russian Grand Dukes, were generally called "Grand Duchesses" in English.
The title Magnus Dux or Grand Duke was used by the Jagiello rulers of Lithuania, who also became kings of Poland. In 1582 king John III of Sweden added "Grand Duke of Finland" to the subsidiary titles of the Swedish kings, however without any factual consequences. The Swedish kings of the Vasa dynasty, who then became kings of Poland as well, also used the grand ducal title for their non-Polish territory. After the Russian conquests, it continued to be used by the Russian Emperor in his role as ruler of Lithuania (1793-1918) and of autonomous Finland (1809-1917) as well. The Holy Roman Empire ruling house of Habsburg instituted a similar Grand Duchy in Transylvania in 1765.
The title Grand Duke has also been used by rulers of several states within the Germanic Confederation:
The title was also used in some short-lived Napoleonic creations: