John Joseph O'Kelly (known as Sceilg; 4/7 July 1872 – 26 March 1957) was an Irish politician, author and publisher. He was a president of the Gaelic League and of Sinn Féin.
Born John Kelly in Coramore, on Valentia Island off the County Kerry coast, he was the son of Patrick Kelly, a farmer, and Ellen Sullivan. While his birth date is recorded as 7 July 1872, his family gave it as 4 July.
He joined Sinn Féin at its inaugural meeting on 5 November 1905. Following the 1916 Easter Rising, O'Kelly joined the Irish Nation League and became treasurer of the Irish National Aid and Volunteers' Dependants' Fund for the relief of prisoners and their families. In February 1917 he was arrested and deported to England where he was interned without trial for several months. On his release O'Kelly was elected to the Provisional Committee of the newly merged Irish Nation League and Sinn Féin, thereafter called Sinn Féin. He was appointed editor of the influential "Catholic Bulletin". In the 1918 general election he was elected as a Sinn Féin MP for Louth by 255 votes in what was the closest contest in Ireland in that election. The closeness of the contest was due to the strong AOH organisation in the county that campaigned for outgoing North Galway MP Richard Hazleton of the Irish Parliamentary Party.
O'Kelly took his seat in Dáil Éireann as a Sinn Féin Teachta Dála and was Leas-Cheann Comhairle (Deputy chairman) from 1919–21. He was Secretary for Education in the Government of the 2nd Dáil. From 1919 to 1923, he was President of the Gaelic League. He opposed the Anglo-Irish Treaty that was ratified by the Dáil in January 1922, and refused to accept the legitimacy of the Irish Free State established in December 1922. He and others maintained that the Irish Republic continued to exist and that the rump of the Second Dáil, composed of those anti-Treaty TDs who had refused to take their seats in what became the Free State parliament, was the only legitimate government for the whole of Ireland. In June 1922, he was elected to the Third Dáil for the constituency of Louth/Meath but abstained from taking his seat. In August 1923, standing as a Republican for the Meath constituency, he was defeated for an abstentionist seat in the 4th Dáil. He was again defeated in the Roscommon by-election of 1925, his last election attempt. After the resignation of Éamon de Valera as president of Sinn Féin in 1926, O'Kelly, who maintained an abstentionist policy towards Dáil Éireann, was elected in his place and remained in this position until 1931 when Brian O'Higgins took over the leadership.