Like many northern families, the O'Donnells of Tir Conaill were part of the great Ui Neill tribal grouping, claiming common descent from Niall Noigiallach, Niall of the Nine Hostages, the fifth-century monarch who is reputed to have kidnapped St. Patrick to Ireland, and are the best known of the Cenel Conaill, those descended from Conall, one of the sons of Niall; it is from Conall that Tir Conaill ("Conall's country") derives. The O'Donnells were not prominent in early times, inhabiting a relatively small territory around Kilmacrenan. From the late middle ages, however, their power and influence grew steadily until, by the fourteenth century, they were undisputed lords of Tir Conaill, roughly identical to modern Co. Donegal.
Their dynasty continued for more than three centuries, culminating with their involvement in the Nine Years War, in which Red Hugh O'Donnell (1571-1602) and his brother Rory, First Earl of Tyrconnell (1575-1608) played a famous part, almost inflicting a decisive reverse on the progress of English rule. The defeat suffered by the alliance of the remaining pre-eminent Gaelic families was the beginning of the end for the old order in Ireland. Rory O'Donnell was one of those who took part in the "Flight of the Earls", the departure from Lough Swilly in Donegal in 1607 of the most powerful remaining Irish leaders.
Unlike many others among the old Irish aristocracy, however, the line of their descent remains unbroken however. The last duly inaugurated Chief was Niall Garbh ("Rough"), and a direct line of succession from his younger brother Hugh Buidh ("Yellow") continues down to the present. The present "O Donnell of Tirconnell", recognised as such by the Chief Herald of Ireland, is Aodh O Donnell, now living in Dublin.
The arms illustrated are those of Sir Hugh O'Donnell, father of Red Hugh and Rory. They are based on an incident recorded in two of the Lives of St. Patrick, according to which the saint, having converted Conall, the ancestor of the O'Donnells, rewarded his zeal by marking on his shield the sign of the Cross and instructed him and his descendants to wear it thereafter as the emblem of victory. Although no motto is associated with Sir Hugh's arms, many of the other branches of family have reinforced the message with the motto "In hoc sgno vinces", in this sign you will win.
James Louis O?Donnell (1738-1811) was Prior of the Franciscans in Waterford and was sent from there to minister to the spiritual needs of the many Waterford emigrants in Newfoundland. He became known as the "Apostle of Newfoundland"
Peadar O?Donnell (1893-1986), writer and socialist, was Ireland?s best-known and most influential dissident from the 21930s to the 1960s.
Mary O?Donnell (b.1954) has published poetry, fiction and criticism and is regarded as one of the best contemporary Irish writers.