Born Johanna Sheehy, daughter of an Irish Party MP, she was asked while a university student to sign a petition for women’s suffrage and “became a conscious suffragist”.
She joined the Irish Women’s Suffrage and Local Government Association, together with Francis Skeffington, who she married in 1903, their shared surnames signifying the equality of their relationship. He resigned as registrar of the National University in protest at its treatment of women. In 1908, “in a hurry with reform”, the couple co-founded, with Gretta and James Cousins, the Irish Women’s Franchise League (IWFL), as a militant suffrage organisation. Francis and James edited the IWFL’s newspaper The Irish Citizen. In June 1912 Hanna was among the first group of IWFL members to undertake militant action, receiving two months imprisonment for smashing windows in Dublin Castle. She lost her teaching job and was imprisoned again in 1913 for protesting against Edward Carson.
She supported the ideals of the Easter Rising, delivering food and messages to outposts. Following her husbands murder she toured the US in support of Sinn Féin. Forbidden by the British to return to Ireland, she was arrested and imprisoned in Holloway prison, winning release through hunger strike. She resumed work on The Irish Citizen and in 1919 became organising secretary of Sinn Féin. She opposed the Treaty, leafletting Dáil Éireann to extend the franchise to women over 21. She opposed the 1937 Constitution and in 1943 stood unsuccessfully as an independent, hoping a women’s party would emerge.