Giselbert of Luxembourg was count of Salm and of Longwy, then count of Luxemburg from 1047 to 1059. He was the son of Frederick of Luxembourg, count of Moselgau, and perhaps of Ermentrude of Gleiberg.
At first count of Salm and of Longwy, on his brother Henry II's death he inherited the county of Luxembourg, as well as providing the income for the abbeys of Saint-Maximin in Trier and Saint-Willibrord in Echternach. He got into an argument with the archbishop of Trier Poppon as to the abbaye Saint-Maximin, which was arbitrated by his brother Adalbero III, bishop of Metz.
In 1050, since the population of the town of Luxembourg had risen considerably, he expanded the city by building a new fortified wall around it.