Nazi concentration camps in Norway (Norwegian: konsentrasjonsleirer) were concentration camps or prisons in Norway established or taken over by the Quisling regime and Nazi German authorities during the German occupation of Norway that began on 9 April 1940 and used for internment of persons by the Nazi authorities. 709 prison camps or concentration camps, [including some death camps,] were counted by a project that had Randi Bratteli (author and widow of former prime minister and concentration camp prisoner), as an advisor. Another source has claimed that there were around 620 prison camps.