Maria "Mimi" Terwiel was a German resistance fighter against the Nazi regime. She was active in a group in Berlin that wrote and distributed anti-Nazi and anti-war appeals. As part of what they conceived as a broader action against a collection of anti-fascist resistance groups in Germany and occupied Europe that the Abwehr called the Red Orchestra, in September 1942 the Gestapo arrested Terwiel along with her fiancée Helmut Himpel. Among the leaflets and pamphlets they had copied and distributed for the group were the July and August 1941 sermons of Clemens August Graf von Galen which denounced the regime's Aktion T4 programme of involuntary euthanasia.

The Red Orchestra, as it was known in Germany, was the name given by the Abwehr Section III.F to anti-Nazi resistance workers in August 1941. It primarily referred to a loose network of resistance groups, connected through personal contacts, uniting hundreds of opponents of the Nazi regime. These included groups of friends who held discussions that were centred on Harro Schulze-Boysen, Adam Kuckhoff and Arvid Harnack in Berlin, alongside many others. They printed and distributed prohibited leaflets, posters, and stickers, hoping to incite civil disobedience. They aided Jews and resistance to escape the regime, documented the atrocities of the Nazis, and transmitted military intelligence to the Allies. Contrary to legend, the Red Orchestra was neither directed by Soviet communists nor under a single leadership. It was a network of groups and individuals, often operating independently. To date, about 400 members are known by name.