Sigurd Hart (800-855) was the son of Helgi the Sharp and Aslaug, the husband of Thyra Haraldrsdottir, and the father of Ragnhild Sigurdsdotter. At the age of 12, he slew the berserker Hildibrand and 11 other men in a duel, and he married the daughter of the Jutish chieftain Harald Klak and had two children: Ragnhild and Guthrum. In 855, he was murdered by the berserker Hake, who abducted Ragnhild.