Jakob Weidemann was a Norwegian artist. Jakob Weidemann is regarded as one of Norway's more important artists of post-war Modernism. Weidemann's work Storfuglen letter (1959) was selected as one of the twelve most important Norwegian artworks by Morgenbladet.
Weidemann was born at Steinkjer in Nord-Trøndelag, Norway. He was the son of Osvald Weidemann (1902–1965) and Therese Margrethe Opdahl (1905–1990). He was born out of wedlock and spent the first years of childhood with his mother's parents at Steinkjer. His mother was married in 1930 to Einar Johansen (1907–1982) who was life insurance inspector and later art dealer. Weidemann moved to Oslo at age 11 to live with his mother and step-father. In 1939, the family moved to Bergen. He was educated under Eivind Lundboe at the Bergen Art School (Bergen Kunsthåndverkskole) (1939), trained with artist Ole B. Eyde in Bergen (1940–41) and studied at the Norwegian National Academy of Fine Arts in Oslo under Axel Revold and Søren Onsager (1941–42). He was awarded a Government travel allowance in 1952 and received the Conrad Mohr's legacy in 1955. He conducted study trips to Copenhagen in 1946; Paris in 1949; Italy in 1955; and the Netherlands in 1958.
His first solo exhibition was at Paus Knudsens Kunsthandel in 1942. Weidemann joined the Norwegian resistance movement during the Occupation of Norway by Nazi Germany, was arrested but escaped to Sweden in 1944. While there he was the victim of an accident in which an explosive charge blew up in such a way that he was blinded. He regained his sight, but then only in the left eye. The experience of being blind may have been decisive for the direction his art was later to take – towards an explosion of color and light.
Jacob Weidemann pioneered abstract painting in Norway in the decades following the Second World War. His first exhibition at Blomqvist's Fine Art (Blomqvists kunsthandel) in Oslo during 1946 was his breakthrough. Weidemann is considered to have been become one of the more influential artists within Norwegian modernism in the 1950s. After some experimentation with different styles in the 1940s and 1950, Weidemann finally settled in what can be called expressive, lyrically abstract art. Abstract expressionism with nature as inspiration and basis became characteristic of work by Weidemann.