Lotharingia was a medieval successor kingdom of the Carolingian Empire, comprising the Low Countries, the western Rhineland, the lands today on the border between France and Germany, and what is now western Switzerland. It was named after King Lothair II.It was born of the tripartite division in 855, of the kingdom of Middle Francia, itself formed of the threefold division of the Carolingian Empire by the Treaty of Verdun in 843.