àSeachnasaigh, O'Shaughnessy, collectively UàSheachnasaigh, clan name Cinél nAedha na hEchtghe, is a family surname of Irish origin. The name is found primarily in County Galway and County Limerick. Their name derives from Seachnasach mac Donnchadh, a 10th-century member of the UàFiachrach Aidhne, which the àSeachnasaigh were the senior clan of. The town of Gort, Ireland, was the main residence of the family since at least the time of their ancestor, King Guaire Aidne mac Colmáin.
Up until the late 17th century the àSeachnasaighs held the sub-district of UàFiachrach Aidhne known as Cenél ÃÂeda na hEchtge (modern Irish, Cinéal nAedha na hEchtghe), meaning "kindred of Aedh of the Slieve Aughty", which was also their clan name. Cinéal nAedha na hEchtghe / Kinelea consisted roughly of the civil parishes of Beagh, Kilmacduagh and Kiltartan and also parts of the civil parishes of Kibeacanty and Kilthomas. Their closest related kinsmen were the àCathail / O Cahill clan, originally chiefs of eastern Kinelea, and the other clans of UàFhiachrach Aidhne the most prominent of which were the àhEidhin / O Hynes, àCléirigh / O Cleary and Mac Giolla Cheallaigh / Kilkelly septs. Up until the mid-17th century, the O'Hynes clan were still styled lords of UàFhiachrach Aidhne even though the àSeachnasaighs had become more powerful than their kinsmen during this century. In the 1690s, Captain Roger O'Shaughnessy had his lands confiscated for supporting the Jacobite cause against William of Orange, with the lands going to Sir Thomas Prendergast, 1st Baronet. A legal battle raged on into the first half of the 18th century between the àSeachnasaigh and the Prendergasts, the family who were granted the lands, with the àSeachnasaigh eventually losing the case. The senior line of the àSeachnasaighs may have died out in the 1900s.
O'Shaughnessy castles include Gort Castle, Fiddaun Castle, Ardamullivan Castle, Newtown Castle, Derryowen, which is just inside the County Clare border, Ballymulfaig, and a castle on one of the islands in Lough Cutra. According to a list naming the castles of County Galway and their owners, drawn up in 1574 by the English administration in Ireland, Islandmore Castle (now Thoor Ballylee) was listed as being owned by a John O'Shaughnessy.
The last de facto ÃÂ Seachnasaigh lord of Kinelea died at Gort after returning home from the Battle of Aughrim on 12 July 1691. Thousands of bearers of the name still survive both in their homeland and further abroad.
Notable people with this surname include:
Some with relation to the O'Shaughnessy clan may spell it O'Shaughnessey or Shaughnessy.