She was born in Ripple, Kent. Her brother, John French, would become Lord Lieutenant of Ireland. She expressed regret of her lack of education although she attended a finishing school in London. She married businessman Maximilian Carden Despard, but was widowed when he died in 1890. They had no children. Her romantic novels included Chaste as Ice, Pure as Snow.
Despard was shocked by the levels of poverty in London, where she lived as a child. Following her husband's death she devoted her time and money to helping the poor in Battersea. She lived above one of her welfare shops during the week and converted to Roman Catholicism. She was elected as a Poor Law Guardian for Lambeth poor-law union.
At the time Despard was a vocal supporter of the Social Democratic Federation and the Independent Labour Party. In 1906 she joined the NUWSS (National Union of Women’s Suffrage Societies) and was imprisoned twice in Holloway gaol. She became frustrated with the lack of progress the organisation was making she joined the more radical WSPU (Women’s Social and Political Union).
Eventually, Despard was one of three women who formed the Women's Freedom League after disagreements over the autocratic way in which the WSPU was run. She was joined by Teresa Billington-Greig and Edith How-Martyn. She was closely identified with new passive resistance strategies including women chaining themselves to the gate of the Ladies' Gallery in the Palace of Westminster; and also a "No taxation without representation" campaign which saw her household furniture repeatedly seized in lieu.
Despard spend a lot of time in Frenchpark, County Roscommon, where her father was born. In 1908 she joined with Hanna Sheehy-Skeffington and Margaret Cousins to form the Irish Women’s Franchise League. She urged members to boycott the 1911 Census and withhold taxes and provided financial support to workers during the Dublin labour disputes.
In 1909 Despard met Mahatma Gandhi and was influenced by his theory of passive resistance. She settled in Dublin after World War I and was bitterly critical of her brother, Field Marshall Sir John French.
During the Irish War of Independence, together with Maud Gonne, she formed the Women's Prisoners' Defence League to support republican prisoners. As a member of Cumann na mBan she opposed the Anglo-Irish Treaty, and was imprisoned by the government during the Irish Civil War.
She was buried in the Republican Plot at Glasnevin Cemetery in Dublin.
- An unhusbanded life: Charlotte Despard: suffragette, socialist, and Sinn Feiner by Andro Linklater, Hutchinson, London, 1980.