Christian Fredrik Monsen (27 April 1878 – 31 January 1954) was a Norwegian politician for the Labour Party and the Communist Party. He was born in Kristiania as a son of Ludvig Monsen (1854–1942) and Josefine Aurora Marcelie Dehn (1852–1942). Monsen headed the Ministry of Defence during the short-lived Hornsrud's Cabinet in 1928 and then during Nygaardsvold's Cabinet. Unusually for a Minister of Defence, Monsen was an antimilitarist and wrote three anti-militarist pamphlets (Sannheten om militærvesenet, Avvæbning eller militarisme and Militært vanvidd eller civil fornuft).