Mary Devenport O'Neill (1879-1967) studied at the National College of Art in Dublin. She published two verse plays, Bluebeard (1933) and Cain (1945) and one collection of poetry, Prometheus and Other Poems (London: Jonathan Cape 1929). She also published regularly in The Dublin Magazine up to 1949. Bluebeard, a ballet, based on her play was choreographed by Ninette de Valois as one of the final productions of the Abbey school of ballet in the year it was published. Her work shows the influence of W. B. Yeats and the Imagists, and she is one of a very small number of early 20th century Irish modernist women poets.

Her regular Thursday salon was attended by W. B. Yeats, AE, and other prominent Irish writers. She had a reputation as a psychic and served as consultant to Yeats while he was working on his book A Vision.

Her husband, Joseph O’Neill was Permanent Secretary of the Department of Education and Yeats, in his role as a member of Seanad Éireann, learned a lot about the Irish education system from the O'Neills.