Lotharingia was a kingdom in western Europe, named after Lothair, King of Lotharingia (reigned 855-869), who received it in 855 from his father, Lothair I (795-855), Holy Roman Emperor.
It comprised (broadly speaking) the present:
Lotharingia did not survive its king and became the duchy of Lorraine; it was subdivided and became the object of territorial disputes between France and Germany. The name survives today in the name derived from it: Lorraine (in German: Lothringen).
See also: European region Lotharingia (German/French) (http://www.lotharingia.de)