Mary Teresa Hayden was an Irish historian, Irish language activist and campaigner for women's causes.

Mary Hayden was educated initially at the Dominican College, Eccles Street and then at Alexandra College in Dublin. She attended the Royal University of Ireland

Royal University of Ireland

The Royal University of Ireland was founded in accordance with the University Education Act 1879 as an examining and degree-awarding university based on the model of the University of London. A Royal Charter was issued on April 27, 1880 and examinations were opened to candidates irrespective of...

 where she graduated with a BA(1885) and an MA(1887) in Modern Languages.

A campaigner for gender equality and noted as a public speaker she was a prominent member of the Irish Women's Suffrage and Local Government Association. She was a member of the Gaelic League and friends with Padraig Pearse.
In 1911 she was elected to the senate of the National University of Ireland

National University of Ireland

The National University of Ireland , , is a federal university system of constituent universities, previously called constituent colleges, and recognised colleges set up under the Irish Universities Act, 1908, and significantly amended by the Universities Act, 1997.The constituent universities are...

 and appointed Professor of History at University College Dublin

University College Dublin

University College Dublin ) - formally known as University College Dublin - National University of Ireland, Dublin is the Republic of Ireland's largest, and Ireland's second largest, university, with over 1,300 faculty and 17,000 students...

 in 1915 until her death, she was succeeded by Robert Dudley Edwards

Robert Dudley Edwards

Robert Walter Dudley Edwards was an Irish historian.-Biography:Robert Walter Dudley Edwards, known to his friends as Robin and his students as 'Dudley' was born in Dublin. His father was Walter Dudley Edwards, a journalist who came to Ireland with his wife, Bridget Teresa MacInerney from Clare,...

as chair of Modern Irish History.

Publications

• A Short History of the Irish People by Mary Hayden and George Moonan(1921)
• Diaries of Mary Hayden 1878-1903 edited by Conan Kennedy (National Library of Ireland/Morrigan, 2008)
• The Mysterious Mary H. : A Selection of Writings by Mary Hayden (1862-1942) (Morrigan Books, 2008).