Karl Evang (19 October 1902 – 3 January 1981) was a Norwegian physician and civil servant.
He was born in Kristiania as a son of assisting secretary Jens Ingolf Evang (1873–1914) and Anna Beate Wexelsen (1875–1954). He was a brother of Vilhelm Evang, and a relative of Vilhelm Andreas Wexelsen, Per Kvist and Gunnar Jahn. His sister Anne Beate married another civil servant, Karl Ludvig Bugge. Karl Evang met physician Gerda S. Landmark Moe (1905–1985) in 1926, and married her in 1929.
He enrolled in medicine studies at the Royal Frederick University in 1924, and became a member of the revolutionary group Mot Dag in 1926 which had a strong standing among students. Mot Dag was affiliated with the Communist Party of Norway at the time, but soon became independent. Evang was also active in the Norwegian Support Committee for Spain and Clarté. He was elected chairman of the Norwegian Students' Society in 1931, while serving a prison sentence for conscientious objection. He joined the Norwegian Labour Party after Mot Dag's demise in 1933.
In the 1930s he became a noted public debater. He issued the 1934 book Rasepolitikk og reaksjon, and wrote with the purpose of medicinal and hygienic enlightenment in the publications Populært Tidsskrift for Seksuell Oplysning (which he edited) and Arbeidermagasinet. He was also a popular radio speaker and lecturer. In 1938 he was appointed to the vacant position as director of the Norwegian Directorate for Health. When World War II came to Norway, Evang followed the cabinet Nygaardsvold first to Northern Norway, then to exile in the United Kingdom. Evang was given the rank of lieutenant colonel. He spent the war years organizing a health administration for Norwegians abroad, spending time in the USA as well. After the war he co-founded the World Health Organization; he was also board chairman for some time. His position was strengthened after the war, and Evang signalized technocratic ambitions. Similarly, the health conditions in Norway improved in the post-war years. Poliomyelitis was eradicated and tuberculosis diminished. However, several welfare programs were implemented long after Evang's initiatives. He also had political ambitions (Minister of Social Affairs, probably also Prime Minister) that were never fulfilled.