Guttorm Sigurdsson (Old Norse: Guthormr Sigurðarson) was the King of Norway from January to August 1204, during the Norwegian civil war era. As a grandson of King Sverre, he was proclaimed king by the Birkebeiner party when he was just four years old. Although obviously not in control of the events surrounding him, Guttorm's accession to the throne under the effective regency of Haakon the Crazy led to renewed conflict between the Birkebeiner and the Bagler parties, the latter supported militarily by Valdemar II of Denmark.
Guttorm's reign ended abruptly when the child king suddenly became ill and died. Rumours among the Birkebeiner held that Guttorm's illness and death had been caused by Haakon the Crazy's future wife Christina Nilsdatter, a claim considered dubious by modern historians. Low-intensity civil war followed Guttorm's death, until a settlement was reached in 1207, temporarily dividing the kingdom.
Despite his status as king, Guttorm is not included in the official Norwegian regnal list.