The kings and dukes of Lorraine have held different posts under different governments over different regions, since its creation as the kingdom of Lotharingia by the Treaty of Prüm, in 855.
The Latin construction "Lotharingia" evolved over time into "Lorraine" in French, "Lotharingen" in Dutch and "Lothringen" in German.
After the Carolingian kingdom was absorbed into its neighbouring realms in the late ninth century, dukes were appointed over the territory.
Charles the Bald claimed Lotharingia on Lothair's death and was crowned king in Metz, but his brother Louis the German opposed his claim and in 870 the Treaty of Mersen divided Lotharingia between the two brothers and subsequently their sons.
Upon Bruno's death in 965, these two margraves were recognised as dukes of Lower and Upper Lorraine, respectively.