Ó hUadhaigh, Seán (1886–1959), solicitor, republican, Irish-language enthusiast, and aviation pioneer, was born John Kirwan Woods 20 May 1886 in 2 Brookline, Terenure Rd, Dublin, son of Robert Hewitt Woods (d. 1891), barrister, originally from Co. Down, and Mary Katherine Woods (née Kirwan); he had one sister. His maternal great-grandfather, Thomas Kirwan, was a member of the Catholic Committee in the eighteenth century, and his aunt was married to a brother of Michael Cusack (qv), founder of the GAA. Educated in Dublin at St Mary's College, Rathmines, Blackrock College, and Terenure College, he initially planned to study engineering but chose law instead, and having qualified as a solicitor joined a legal partnership with P. J. Little (qv) and Ernest Proud which later became Little, Proud, & Ó hUadhaigh. A member of the IRB and joint secretary, with Tom Clarke (qv), of the republican Wolfe Tone Club, in the 1918 general election he acted as election agent for George Gavan Duffy (qv) in Dublin County South, and during the war of independence ‘acted as a sort of unofficial attorney general to Dáil Éireann’ (Kotsonouris, 32), defending republican prisoners, including Kevin Barry (qv). In 1920 his office in Eustace St. was ransacked by Black and Tans and he was arrested and imprisoned. During the civil war he took the anti-treaty side and until 1930 was a member of the standing committee of Sinn Féin, after which he became associated politically with Fianna Fáil.
Interested in the Irish language from childhood, when he was a member of the Mount Argus branch of the Gaelic League he frequently travelled to Connemara to learn Irish. From the 1920s he was active in the language revival movement as a member of the Gaelic League's coiste gnótha (executive committee), head of its public administration sector, its solicitor, and president and vice-president of the oireachtas. He was also president of the Gaelic dramatic group An Comhar Drámaíochta and president and founder of Coiste na bPaistí, which arranged Gaeltacht visits for Dublin children. In the 1920s, as a member of Kingstown urban council, he was influential in having the name of Kingstown changed to Dún Laoghaire. Around this time he changed his name by deed poll from Woods to the Irish version Ó hUadhaigh.
Noted as a pioneer of civil aviation in independent Ireland, he was a member and chairman of the Irish Aero Club and in 1935–6 played an important role in the establishment of Aer Lingus, of which he was a director and chairman, and may have been responsible for devising its name; he was also a director of Aer Rianta. Among other positions he held were president of the Incorporated Law Society and doyen of the Faculty of Notaries Public.
He married Mary (‘May’) Dixon; they had two sons and two daughters and lived in Killiney, Co. Dublin. Both of his sons, Robert (below) and Seán Antoine, entered the legal profession. He died 24 January 1959 at St Luke's Hospital, Dublin, leaving an estate of £4,396.
His son Robert (Roibeard,‘Bob’) Ó hUadhaigh (1914–95), lawyer and judge, was born 24 April 1914 in Dublin. Following his father into the legal profession, he became a successful criminal prosecutor for the state, enjoying particular favour while Fianna Fáil were in government in the 1940s. In the 1940s he was also a member of Dún Laoghaire borough council. During 1947–9 he acted frequently as replacement justice for district justices on sick leave in the western district, and in June 1949 was appointed a permanent district justice, and served in Donegal, Leitrim, and Dublin until his retirement in 1984. Possessed of traditional, old-fashioned, and politically incorrect opinions, he became famous in the 1970s when the proceedings of his court were frequently reported in Nell McCafferty's ‘In the eyes of the law’ column in the Irish Times, which highlighted his abrupt manner, demands for appropriate behaviour by all attending his court, and conservative social opinions, but also his wit and humour. Tough on violent crime in particular, he often showed sympathy to young offenders or those in difficult circumstances who appeared before him, and he did not always take the side of the state, especially if he felt a case had not been adequately prepared or if there was insufficient evidence of an offence. On one occasion when a garda, who had arrested a drunken person for an alleged breach of the peace, complained: ‘Justice, he told me to eff off’, he dismissed the case with the curt response: ‘And why didn't you?’ He married (24 September 1940) Marie Kelly of Chapelizod, Dublin, daughter of Joseph Kelly, baker; they had three daughters and one son. He died 1 December 1995 at the Mater private hospital, Dublin.