The County of Luxembourg was a State of the Holy Roman Empire. It arose from medieval Lucilinburhuc Castle in the present-day City of Luxembourg, purchased by Siegfried, Count of the Ardennes in 963. His descendants of the Ardennes–Luxembourg dynasty 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 the Holy Roman Empire.

Sigfried was count in the Ardennes, and is known in European historiography as founder and first ruler of the Castle of Luxembourg in 963 AD, and ancestor and predecessor of the future counts and dukes of Luxembourg. He was also an advocate of the abbeys of St. Maximin in Trier and Saint Willibrord in Echternach.