A former kingdom of western Europe west of the Rhine River. Created in the partition of the Carolingian Empire in the 9th century, Lotharingia was split in the 10th century into the duchies of Lower Lotharingia (in the present-day Low Countries and northwest Germany) and Upper Lotharingia (present-day Lorraine).
Received the northern part of his father's domain, known as Lotharii or Hlutharii Regnum, corrupted later into Lotharingia or Lorraine.
843 the Rhine formed the boundary between Germany and the middle kingdom of Lotharingia; but by 870 it lay wholly within the former realm.
Rather than acknowledge him, the duke of Lotharingia-, or Lorraine, transferred his allegiance to Charles the Simple of France; and it was in vain that Conrad protested and despatched armies into Lorraine.
In 843, by the treaty of Verdun, it became part of Lotharingia (Lorraine), and in 879 was annexed to the kingdom of East Francia (Germany) by the treaty of Meerssen.
However, asthe boundary between the possessions of Charles the Bald and those of Louis was not strictly defined, and as Lothairs kingdom, having no national basis, soon disintegrated into the kingdoms of Italy, Burgundy and Arles, in Lotharingia, this great undefined territory was to serve as a tilting-ground for France and Germany on the very morrow of the treaty of Verdun and for ten centuries after.