MATHILDE, daughter of --- ([1025/26]-Paris 1044, bur église de l'Abbaye royale de Saint-Denis). Rodolfus Glaber records that King Henri married "Mathildem…de regno eius ex Germanie nobilioribus"[229]. Her precise origin is not known. A manuscript entitled "Excerptum Historicum" records the marriage of "rex Henricus" and "neptem Henrici Alamannorum Imperatoris", commenting that the couple had a daughter who died young and that King Henri's wife died soon after[230]. The Historia of Monk Aimon records that King Henri married "neptem Henrici Alamaniæ Imperatoris" in 1034[231]. Szabolcs de Vajay[232] suggests that she was Mathilde, daughter of Liudolf Markgraf von Friesland [Braunschweig] & his wife Gertrud von Egisheim, her supposed father being the uterine half-brother of Emperor Heinrich III. The Historia Francica records the death in 1044 of "Mahildis Regina"[233]. The Miracula Sancti Bernardi records the death in Paris in 1044 of "Mahildis regina…ex Cæsarum progenie", and her burial "monasterio Sancti Dionysii"[234].
Mathilde de Frise (v.1024-1044), reine de France, fille de Luidolf de Frise et de Gertrude d'Eguisheim, nièce de Bruno, évêque de Toul qui est élu pape en 1049 sous le nom de Léon IX.
http://fr.wikipedia.org/wiki/Mathilde_de_Frise