Callan, Margaret (née Hughes) (Thornton MacMahon) (c.1817–c.1883), writer, teacher, and nationalist, was born in Newry, Co. Down, the daughter of Phillip Hughes, a local flax buyer, and his wife, Susan Gavan, of Latnamard, Co. Monaghan, the aunt of Charles Gavan Duffy (qv). She was one of a large and talented family, and the death of her father when she was eighteen forced her to begin supporting herself. Helped by her sisters, she established in 1835 a boarding school for girls in Blackrock, Co. Dublin. Advertised in the Nation, the school was successful, and Callan attempted to inspire her pupils with the nationalist ideals of the Young Irelanders. She married John B. Callan, MD, of Stephen's Green, Dublin, a pharmaceutical chemist and apothecary and an occasional contributor to the Nation, whose business premises were located on Merrion Row.
Callan's family connections closely involved her in the Young Ireland movement. In 1846 her cousin Gavan Duffy married her sister Susan (d. 1880), a highly accomplished musician reported to have studied under Liszt and Chopin. Callan, as well as her brother Terence MacMahon Hughes, wrote for the Nation, though only two articles can certainly be attributed to her: ‘A day at Versailles’ (29 July 1843) and ‘A day in Paris’ (9 Sept. 1843). In these she wrote of the strong support in France for Daniel O'Connell (qv) and the repeal of the act of union. Under the pseudonym Thornton MacMahon, she edited The casket of Irish pearls (1846), a collection of Irish verse and prose for the Library of Ireland series published by James Duffy (qv). Her introduction to this anthology, dedicated to ‘the young men of Ireland’, called on them to show their readiness for self-government by organising and educating themselves. When the Irish Confederation began to break down in the early summer of 1848, two of Callan's former students volunteered to act as messengers, but Gavan Duffy, believing the situation to be too fraught for young women, declined the offer. Following Duffy's imprisonment in Newgate in July 1848, Callan, together with Jane Francesca Elgee (qv), temporarily assumed editorial control of the Nation. Described by Gavan Duffy as ‘a woman of genius’ (Four years, 681), through him she became acquainted with Thomas Carlyle when he visited Ireland in 1847.
In 1856 the Callans emigrated to Australia, where their daughter Margaret later married Gavan Duffy's eldest son by his first marriage. Callan seems to have maintained a close interest in Ireland, although she did not wish to return; among her correspondents was her friend William Carleton (qv), to whom she wrote: ‘I would not go back if I could, and daily thank God, especially when I happen to read a Nation (or, indeed, any Irish journal), that my children are safe beyond the dangers of starvation or flunkeyism’ (O'Donoghue, ii. 297). She died in Melbourne in about 1883.