Lambert (died 1140 or after), Count of Montaigu and Clermont, son of Conon, Count of Montaigu, and Ida of Boulogne. Lambert was also Seigneur de Rochefort, Avoué of Dinant, and Avoué of Saint-Symphorien-des-Bois.
As reported by both Albert of Aix and William of Tyre, Lambert and his brother Gozelo took a major role in the First Crusade, participating in the Siege of Nicaea in 1097. Lambert was present at the siege of Acre in 1098, which finally fell after four years. He commanded one of the corps of the army of Robert II, Count of Flanders, resulting in the capture of Antioch in 1098. Along with his father and Peter the Hermit, he founded the Neumoustier Abbey.
Lambert was married although there is some confusion as to his wife. Europäische Stammtafeln lists two possibilities. First is Gertrud de Louvain, daughter of Henry III, Count of Louvain, and Gertrude of Flanders. Second is an unnamed daughter of Giselbert, Count of Clermont. The speculation on the second possibility is based on the connection between Lambert and the Counts of Clermont, but that connection is best explained by his paternal grandmother’s relationship with Clermont. Lambert and his wife (presumed to be Gertrud) had three children:
Upon his death, Lambert was succeeded as Count of Montaigu by his son Godefroi.