McGarry, Seán (1886–1958), revolutionary nationalist, politician, and businessman, was probably born 2 August 1886 at 17 Pembroke cottages, Dundrum, Co. Dublin, one of at least five sons and five daughters of John McGarry, a letter carrier, and his wife Mary (née Kelly). He worked closely with Bulmer Hobson (qv) and Denis McCullough (qv) on the revival (from c.1905) of the IRB, engaged in organisation of the secret society in the Dublin area. He was associated with Seán Mac Diarmada (qv) on the publication of the IRB organ, Irish Freedom (1910–14), and managed a Belfast-based paper, the Republic. A founding member of the Irish Volunteers (1913), he edited the memorial publication to Jeremiah O'Donovan Rossa (qv) (1915). He was among the select number informed by MacDiarmada and Thomas Clarke (qv) at a meeting in September 1914 of the decision of the IRB supreme council to stage an armed rising during the course of the European war. A Volunteer captain, he served on headquarters staff in the GPO during the 1916 Easter rising as ADC to Clarke. Among the last to evacuate the burning building on Friday 28 April, while sharing a last meal with several comrades and a priest from the pro-cathedral, he quipped that he for one was prepared to risk damnation by eating meat on a Friday. Sentenced by court-martial to death, commuted to eight years’ penal servitude, he was imprisoned in Mountjoy, Portland, and Lewes jails, until his release in the June 1917 amnesty.
Named to the supreme council of the reconstituted IRB, McGarry was among the several key IRB activists (including Michael Collins (qv)) elected to the Irish Volunteers executive at the October 1917 secret convention, thereby securing a decisive IRB influence within the paramilitary body. As Volunteers general secretary (a post he occupied until June 1922), he was prominent in the vigorous implementation of recruitment, training, and arming. Sometime in the autumn of 1917, McGarry succeeded Thomas Ashe (qv), who had died in prison on hunger strike on 25 September, as president of the IRB supreme council – thereby becoming, under the organisation's constitution, president of the Irish republic virtually established. He was arrested in his home during the ‘German plot’ round-up of nationalist leaders (17–18 May 1918); Collins, arriving late with a warning, evaded arrest himself by passing the night in the already raided house. Imprisoned in Lincoln jail, after assisting in detailed planning and procurement of a duplicate key, McGarry joined Sinn Féin president Éamon de Valera (qv) and Sean Milroy (qv) in effecting a dramatic prison escape (3 February 1919). Returning clandestinely to Ireland, he made a sensational public appearance at the Dublin Mansion House, introduced to a concert audience from the stage. Although during his imprisonment he had been replaced as IRB president by Harry Boland (qv), McGarry remained prominent in the upper echelons of both the IRB and Sinn Féin, sitting on the latter body's ard-comhairle, and was a captain in the IRA Dublin Brigade throughout the war of independence. An electrician by trade, he was among several republican ex-prisoners to establish themselves in business on monies received from the Irish National Aid Association.
McGarry served on Dublin Corporation (1920–24), first as councillor and then as alderman, until the city council's dissolution by ministerial directive (May 1924). As Sinn Féin TD for Mid Dublin (1921–3), he supported ratification of the Anglo–Irish treaty, and secured the third Mid-Dublin seat as pro-treaty candidate behind independents Laurence O'Neill and Alfie Byrne (qv) in the June 1922 general election. Also serving as captain in the national army (July 1922–August 1923), during the civil war he was a particular target of anti-treaty hostility owing to his IRB importance. Two days after the summary executions of four prominent republican prisoners in Mountjoy jail, McGarry's home at 37 Philipsburgh Avenue, Fairview, was burned in an IRA raid (10 December 1922); his seven-year-old son Emmet died of injuries suffered in the attack. The following month his electrical fittings shop at 14 St Andrew's St. was bombed. Elected Cumann na nGaedheal TD for Dublin North (1923–4) on the strength of the massive first-count surplus of constituency colleague Richard Mulcahy (qv), McGarry served on a special dáil committee on wireless broadcasting, which rejected proposals for a privately owned Irish service in favour of a service run wholly or dominantly by the state; McGarry declined to sign an interim committee report (January 1924) owing to his business connections with the electrical trade. He was among the nine ‘national group’ TDs who seceded from the pro-treaty parliamentary party in the wake of the 1924 army mutiny, ultimately resigning their dáil seats in protest at the government's handling of the affair (30 October 1924).
Retiring from public life, in later years McGarry was employed by Irish Hospitals Trust, wrote articles for newspapers and journals, and engaged in broadcasting. After residing from the mid 1920s at several addresses in Dún Laoghaire, from 1938 he lived at 25 Booterstown Avenue, Blackrock. With his wife Tomasina (d. 1957) he had two sons and one daughter. He died suddenly 9 December 1958 of a heart attack in his son's home at 44 Richmond Avenue, Monkstown, Co. Dublin.