Hayden, Mary Teresa (1862–1942), historian and women's rights campaigner, was born 19 May 1862 in Merrion Square, Dublin, only daughter of Thomas Hayden (qv), physician and later vice-president of the Royal College of Surgeons, and Mary Anne Hayden (née Ryan; d. 1871). She was first educated at Mount Anville convent, Co. Dublin, and the Ursuline convent, Thurles, Co. Tipperary. She attended Alexandra College at Earlsfort Terrace, Dublin, where she graduated BA (RUI) in modern languages (1885) and took a master's degree (1887). In the course of the next few years she travelled widely, including trips to Greece, India, and America; worked as a tutor in some of the women's colleges; and in 1895, by examination, was awarded a junior fellowship in English and history from the RUI. She applied for a senior fellowship four times but was refused; had she been a male she would have been entitled to lecture in history, and her diaries contain wry entries about the status of an unhired female scholar at this time.
With Agnes O'Farrelly (qv) (Úna Ní Fhaircheallaigh) she was foremost in the campaign for women's rights in the universities. She met the Robertson commission in 1901 on behalf of St Mary's Dominican convent, Eccles St., Dublin, where, as well as presenting the results of a questionnaire survey of women graduates, compiled in conjunction with O'Farrelly and Hanna Sheehy- Skeffington (qv), she argued for the right of women to receive education on the same terms as men and in the same colleges, and to be employed by the universities on identical conditions (which was not realised until the Irish Universities Act of 1908). Along with Sheehy Skeffington, she was a key figure in the formation (1902) of the Irish Association of Women Graduates, which concerned itself with various questions regarding women graduates’ employment in government departments, hospitals, and schools, as well as attempting to influence public policy in relation to sex discrimination. From 1907 to 1912 she acted as advising examiner in history for the intermediate education board; after the passing of the universities act in 1908, she was appointed a member of both the senate of the NUI and the governing body of the new UCD, the first woman to hold such positions. In November 1909 she was appointed a lecturer in history, and in July 1911 first professor of modern Irish history at UCD, a position she held until her retirement in 1938.
A busy campaigning life outside the university saw her involved with Helen Chenevix (qv) and Louie Bennett (qv) in the formation of the Irish Women's Suffrage and Local Government Association in 1911, the same year in which she chaired the first meeting of the Irish Women Workers’ Union. Regarded as an efficient and impartial chairwoman, she also presided over a mass meeting in June 1912 protesting against the proposed third home rule bill, which did not include suffrage for women. In 1915, along with Mary Louise Gwynn, she founded the Irish Catholic Women's Suffrage Society, and was also active in the Irish Women's Franchise League, which mixed campaigning for the vote with a variety of intellectual pursuits. She also became involved in the Women's International League for Peace and Freedom. Hayden was more moderate a nationalist than contemporary feminists such as Constance Markievicz (qv) and Hanna Sheehy Skeffington, and supported the Irish parliamentary party rather than Sinn Féin. She had developed a friendship with Patrick Pearse (qv) in 1903 through her deep attachment to the Gaelic League; holidayed with him in Connemara, Co. Galway, enjoying long conversations; and later encouraged him not to set his mind so firmly against marriage (she had been engaged for some time, but her fiancé died of tuberculosis). She was also one of the board of governors set up to administer the finances of Pearse's St Enda's College, but she was strongly opposed to the 1916 rising, recording later that she ‘could not in conscience help’ (Edwards, Pearse, 329), and wishing she had had more contact with Pearse in the months before the rising.
As a historian and teacher, while actively involved with students, Hayden did not undertake major research projects. She wrote a number of articles on eighteenth-century Ireland for such publications as Studies, the Dublin Review, and the Journal of the Royal Society of Antiquaries in Ireland. Her most significant publication was a textbook on Irish history with G. A. Moonan (1872–1945) (Hayden in fact wrote most of it), A short history of the Irish people from the earliest times to 1920 (1921), which became the most widely used survey of Irish history in Irish schools until the late 1960s. The ‘scientific’ approach to the study of Irish history being pioneered from the 1930s by Robert Dudley Edwards (qv) and T. W. Moody (qv) seems to have left her cold, and her distaste for the new developments was implicit in her book reviews. Edwards, who was to be her successor as professor in UCD, praised her short history for its vigorous style and high degree of objectivity, but expressed regret that in later editions her strong personal feelings appeared to influence her treatment of the 1920s.
Hayden continued to pursue political causes, remaining a member of the senate of the NUI until 1924, and in the 1930s represented the National Council of Women in Ireland and the NUI Women Graduates Association in their protests against what were perceived as reactionary economic and social government policies. At the Mansion House, Dublin, in November 1935, representing the National Council of Women, she strongly condemned orthodox state policy and called on the government to provide public works of national utility to create further employment. In some senses she subverted stereotype, suggesting (for example) that women in the home had not enough to do, and using this argument to call for the development of meaningful interests for women outside the home, including public life. Her last major public campaign, at the age of 75, was in the lead-up to the plebiscite on the 1937 constitution, in opposition to articles 40, 41, and 45 concerning the status of women. Reversing her lifelong non-party-political stance, she helped to form the Women's Social and Progressive League as a political party committed to opposing the constitution and any regressive consequences it would entail.
She received an honorary doctorate from the NUI in 1935, three years before her retirement. A dedicated cyclist and swimmer (she learned to dive at the age of 70), Hayden was fluent in Irish, Greek, and Hindustani, and after retirement devoted her efforts to improving the welfare of Dublin children through her newly formed social club. She died 12 July 1942 at her residence in Rathmines, Dublin. Her unpublished diaries are deposited in the NLI.