Sigurd Daniel Isaachsen Willoch (16 May 1903 - 20 March 1991) was a Norwegian art historian and director of the National Gallery of Norway.
[4] He wrote considerably about Norwegian art and artists dating from the 19th century, including works about artists Olaf Isaachsen, Edvard Munch, Hugo Lous Mohr (1889–1970), August Cappelen (1827–1852) and Thomas Fearnley (1802–1842).
He also produced works which focused on the Art Society in Oslo and the National Gallery of Norway.
[2] He was employed as a curator at Akershus Castle in 1937 and held this position until he took over as director of the National Gallery of Norway in 1946.
He served on the National Gallery Board 1952–76, was a member and sometimes chairman of the Norwegian unit of Scandinavian Museum Association 1946–71, Norwegian member of the Comité International d'Histoire de l'Art (CIHA) from 1958 to 1973 and represented Norway for some years in the International Council of Museums.