Mary Sophia Allen (12 March 1878 – 16 December 1964) was a British woman who worked for women's rights. She is chiefly noted as one of the early leaders of the Women's Police Volunteers as well as for her involvement in far right political activity.
Allen was born to a well-to-do family in Cardiff in 1878, one of the ten children of Thomas Isaac Allen, Chief Superintendent of the Great Western Railway. Mary was close to her sisters, all of whom had a tendency to religious mysticism. She was educated at home and later at Princess Helena College. She left home at the age of thirty in 1908 after a disagreement with her father about women's suffrage, and joined Emmeline Pankhurst's Women's Social and Political Union, becoming an organiser in the South West, and later in Edinburgh. She was imprisoned three times in 1909 for smashing windows, twice went on hunger-strike, and was force-fed on the last occasion, for which she was awarded a hunger-strike medal by Emmeline Pethick-Lawrence.
At the outbreak of the First World War, militant suffragist activities ceased. Allen turned down an offer of work with a needlework guild (see for example Queen Mother's Clothing Guild) and looked around for a more active occupation. She heard that a number of women were trying to set up a women's police force and, in 1914, she joined Nina Boyle's Women Police Volunteers. This was taken over by Margaret Damer Dawson in 1915 and renamed the Women Police Service (WPS), with Allen as second-in-command. They designed their own uniform and opened training schools in London and Bristol. They saw their role as mainly dealing with women and children and rescuing women from "vice" (prostitution) and 'white slavery'. Allen served at Grantham and Kingston upon Hull, overseeing the morals of women in the vicinity of army barracks. She went on to police munitions factories which employed large numbers of women. She also worked in London, where 'khaki fever' was perceived as a problem.Child welfare work led the WPS to set up a benevolent department and a home for mothers and babies. Allen was awarded the OBE for services during the War.