Icelandic scholar and statesman who collected and edited many Old Norse sagas and documents. He was also the leader of the 19th-century struggle for Icelandic self-government under Denmark.

Sigurdsson was educated in classical philology, ancient history, and political theory and economics at the University of Copenhagen. He spent much of his life gathering and editing old Icelandic manuscripts as a member and then as secretary of the Arnamagnaean Foundation, which had been established for that purpose. Alone or with others he edited such collections as Íslendinga sögur (vol. 1–2, 1843–47; “Icelandic Sagas”) and Lovsamling for Island (1853–57; “Collection of Icelandic Laws”).

An advocate of Icelandic autonomy under Denmark, Sigurdsson took part in discussions that led to the Danish king Christian IX's restoration of the old Icelandic Althing (parliament) as an advisory body in 1843. Sigurdsson was elected to that body for its first session in 1845, later becoming its speaker. As a leader of the Patriotic Party, Sigurdsson successfully agitated for Iceland's freedom of trade (1854); he also led in the modernization of Iceland's agriculture and fishing techniques. Always pressing Denmark for self-government, he undoubtedly influenced the granting by Denmark in 1874 of a constitution that provided for Iceland's control of its finances and for legislative power shared with the Danish crown.