Joseph O'Sullivan (25 January 1897 – 10 August 1922) along with Reginald Dunne, was a member of the Irish Republican Army, who shot dead Field Marshal Sir Henry Hughes Wilson on his doorstep at 36 Eaton Place in London on 22 June 1922. He was hanged for the killing on 10 August 1922 at Wandsworth Prison. The event provided the inspiration for the film Odd Man Out.
O'Sullivan's father John was originally from Bantry, County Cork, and had moved to London as a young man where he eventually became a successful tailor. O'Sullivan's mother Mary Ann O'Sullivan (née Murphy) was also born in Ireland in Inniscarra, County Cork. O'Sullivan was the youngest of a thirteen children all born in London, although only eleven survived to adulthood. As a boy O'Sullivan attended St Edmund's College, Ware. On 25 January 1915 (his eighteenth birthday) O'Sullivan enlisted into the Royal Munster Fusiliers, and later transferred to the London Regiment. O'Sullivan served as a British Army lance corporal with the London Regiment during the First World War and lost a leg at Ypres in 1917.
On being discharged from the army in 1918, O'Sullivan was employed by the Ministry of Munitions and, when the war ended, was transferred to the Ministry of Labour where he worked as a messenger. The Ministry of Labour was located in Montagu House, which was later demolished and replaced by the present day Ministry of Defence. Montagu House was located adjacent to Scotland Yard and it is probable that O'Sullivan used his position in the civil service to obtain information for the London IRA. On the day of the assassination, O'Sullivan left work at lunchtime and did not return. During the course of his pursuit and capture O'Sullivan shot and wounded two policemen and a civilian.
Joseph O'Sullivan was an active Volunteer with the London IRA and was named by Rex Taylor as being responsible for the shooting of the "spy" Vincent Fovargue on Ashford Golf Links, Middlesex. Fovargue was found dead on the golf course on 5 April 1921 with a label pinned to his body stating "Let spies and traitors beware, IRA". Fovargue was 21 years old when he died and had been an officer in the Dublin IRA. He had been captured and tortured by the Crown Forces and allowed to "escape" after promising he would infiltrate the London IRA.
O'Sullivan's brother, Patrick O'Sullivan, was the first Vice Commandant of the London IRA during its early days in 1919 but was seconded to the Cork No. 1 Brigade for the period of the Anglo-Irish War. Patrick O'Sullivan had also served in the London Regiment during the First World War along with another brother Aloysius, who was discharged from the army in 1916 suffering from shell shock. Patrick O'Sullivan was also wounded in a gas attack during the First World War. Patrick O'Sullivan fought with the anti-Treaty IRA during the Civil War and was wounded in action ten days after his brother was executed. Shortly before that, Patrick had crossed over to England in order to participate in an attempt to rescue the two men. In the year after their execution, John O'Sullivan tried to have the remains of the two men released in order that they could have a proper burial. However, it was only after the abolition of hanging that the law was changed and Patrick O'Sullivan, with the assistance of the Irish National Graves Association, was able to arrange for the bodies of Joseph O'Sullivan and Reginald Dunne to be repatriated to Ireland.
In 1967, after some political and diplomatic debate by the British and Irish governments, the British Government allowed the bodies of Dunne and O'Sullivan to be exhumed. They were subsequently reburied in Deans Grange Cemetery in Ireland. O'Sullivan's brother Patrick and another former comrade Harry O'Brien accompanied the bodies from England to Dublin airport, where Patrick O'Sullivan placed an Irish tricolour flag on Dunne's coffin. This was the same flag that Dunne had placed on the coffin of Terence MacSwiney at Euston Station when his body was returned to Cork in 1920.
- Times Literary Supplement 4 May 2007, p. 12
- Michael Collins: A Life; James Mackay, p. 261