The County of Luxemburg (French: Luxembourg, Luxembourgish: Lëtzebuerg) was a State of the Holy Roman Empire. It arose from medieval Lucilinburhuc ("Little Fortress") Castle in the present-day City of Luxembourg, purchased by Count Siegfried in 963. His descendants of the Ardennes-Verdun dynasty (Wigeriche) began to call themselves Counts of Luxembourg from the 11th century onwards. The House of Luxembourg, a cadet branch of the Dukes of Limburg, became one of the most important political forces of the 14th century, contending with the House of Habsburg for supremacy in Central Europe.
The Duchy of Luxembourg was formed when the counties of Luxembourg, Durbuy, Laroche and Vianden (a vassal county since 31 July 1264), the Marquisat of Arlon, and the districts of Thionville, Bitburg and Marville were combined. Luxembourg was an independent fief of the Holy Roman Empire until 1353, when the Luxembourg emperor Charles IV elevated it to the status of a duchy for his half-brother, Wenceslaus I, Duke of Luxembourg.
Upon the extinction of the Luxembourg dynasty, the duchy passed to the House of Valois-Burgundy in 1443, and then to the Archduchy of Austria in 1482. It was integrated into the Burgundian Circle of the Holy Roman Empire, by Emperor Charles V in the Pragmatic Sanction of 1549. During the French Revolutionary Wars, Luxembourg was annexed to the department of Forêts. Following agreement at the 1815 Congress of Vienna, Luxembourg became a Grand Duchy under the rule of, but not part of, the Kingdom of the Netherlands, after which it joined the German Confederation.