Major Flemming Bruun Muus, DSO (born 21 November 1907, Copenhagen, Denmark – died 23 September 1982, Virum, Denmark) was a Danish author and resistance fighter during the German occupation of Denmark in the Second World War.
In 1942, he was recruited in England by the Special Operations Executive and sent to Denmark in March 1943 as their chief agent.
He was awarded the Distinguished Service Order for his contribution to the resistance movement and assistance with Denmark's liberation by the Allies.
After the war, Muus was arrested by British authorities for embezzlement and surrendered to the Danish.
In June 1946 he was sentenced by a Copenhagen court to two years imprisonment for embezzlement.
He was pardoned after a few months provided he went into voluntary exile from Denmark for five years.
From 1946 to 1949, he and his wife travelled to England, South Africa and Italy before returning to Denmark.