Gertrude Guillaume-Schack (9 November 1845 – 20 May 1903) was a women's rights activist who pioneered the fight against state-regulated prostitution in Germany, where she was born. She met considerable resistance due to the prevailing belief that such matters should not be discussed by respectable people, especially women. She also became active in organizing workers associations for German women, and was linked to the Social Democratic Party (SPD). Her activities and political views caused her to be exiled by the German authorities. She moved to England in 1886, where she became involved in Socialist organizations, but fell out with Friedrich Engels. After leaving the English Socialist League she became involved in theosophy. Refusal to accept medical treatment may have contributed to her