Lothier refers to the territory within the Duchy of Lower Lotharingia, governed by the Dukes of Brabant and their successors after 1190 until the end of the Ancien Régime in 1796.
In 1190, at the Diet of Hall in the abbey of Comburg, the German Emperor Henry VI decided that the Duke of Lower Lotharingia, at that moment Henry I of Brabant, would only have ducal authority within his own Lotharingian territories (the county of Leuven) and his imperial fiefs (the Margraviate of Antwerp, the Landgraviate of Brabant and the domain of the abbey of Nivelles). The title of Duke of Lothier became purely honorific and had no further territorial or judicial authority. A few legal courts of Lothier remained in existence, but they only decided in feudal matters.
Lothier should not be confused with the far greater Lower Lotharingia. It is only applicable to: