He was born in Tromsøysund as a son of headmaster Karl Kristian Gleditsch (1851–1913) and Petra Birgitte Hansen (1857–1913). His family moved to Trondhjem and then Fredrikshald in 1905. From 1913 he lived with his sister Ellen Gleditsch. He was also a nephew of Jens Gran Gleditsch and Kristen Gran Gleditsch, a first cousin of Henry Gleditsch and second cousin of Rolf Juell Gleditsch and Odd Gleditsch, Sr.
He took his examen artium in Kristiania in 1919, enrolled at the Norwegian Institute of Technology and graduated as a civil engineer in 1923. He studied further in France until 1925. He worked for the Norwegian Mapping and Cadastre Authority (then known as Norges Geografiske Oppmåling) while studying, and when he returned from France to Norway in 1927 to work as a research assistant at the Norwegian Institute of Technology, he became a prominent member of the Student Society in Trondheim, Mot Dag and Clarté. He was also active in the Communist Party of Norway, but was excluded in 1929 because of his membership in Mot Dag.
He worked as an editor of science articles in the working class encyclopedia Arbeidernes leksikon from 1932 to 1936, and worked in the publishing house Arbeidermagasinets Forlag in the same period. He also wrote books. From 1936 to 1937 he was a secretary for the Norwegian Support Committee for Spain, which sided with the Second Spanish Republic. He also chaired the Norwegian Students' Society in 1934 and 1937. In February 1934 he married fellow activist Ingrid Margaret Haslund (1908–1996), better known as Nini Haslund Gleditsch.
From 1938 to 1940 he worked for Norges Geografiske Oppmåling in Aker and Oslo. He had to leave Norway in 1940 due to the German occupation of Norway, and was among those who oversaw the flight of the Norwegian National Treasury. He settled in the United Kingdom with his wife, and worked in the Ministry of Defence from 1940 to 1943 and for the Norwegian High Command from 1943 to 1945. He was decorated with the Defence Medal 1940–1945 and was declared a Member of the Order of the British Empire.
After the war, in 1945, he returned to Norway and was appointed director of Norges Geografiske Oppmåling, a position he held until 1971. He chaired the Norwegian Geographical Society from 1949 to 1953. He was also involved in the Norwegian development aid project in Kerala, as chairman of the aid foundation Indiafondet from 1958 to 1962. The first Norwegian development aid project, it has been described as "an experiment for former Mot-Dag-ists". A significant motivation for the project was to please the leftist opposition within the Labour Party in a time of NATO membership and increased spendings on defence.
- Arntzen, Jon Gunnar. "Kristian Gleditsch". In Helle, Knut. Norsk biografisk leksikon (in Norwegian). Oslo: Kunnskapsforlaget. Retrieved 27 January 2010.
- Henriksen, Petter, ed. (2007). "Gleditsch". Store norske leksikon (in Norwegian). Oslo: Kunnskapsforlaget. Retrieved 27 January 2010.
- Nordby, Trond (1989). Karl Evang. En biografi (in Norwegian). Oslo: Aschehoug. pp. 236–237. ISBN 82-03-16250-9.