"Grand Duke (feminine: Grand Duchess) is a European hereditary title, used either by certain monarchs or by members of certain monarchs´ families. In status, a Grand ...
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Duke traditionally ranks in order of precedence below an emperor, king or archduke and above a sovereign prince or sovereign duke. The title is used in some current and former independent monarchies in Europe, particularly:
in the present-day Grand Duchy of Luxembourg
historically by the sovereigns of former independent countries such as: Tuscany (from 1569 to 1860, now part of Italy)
in Baden, Hesse, Oldenburg, Mecklenburg-Schwerin, Mecklenburg-Strelitz and Saxe-Weimar — grand duchies from 1815 to 1918, and all now part of present-day Germany" - (en.wikipedia.org 24.06.2021)