Arthur Joseph Griffith (Irish: Art Seosamh Ó Gríobhtha or Art Ó Gríofa; 31 March 1871 – 12 August 1922) was an Irish writer, newspaper editor and politician who founded the political party Sinn Féin. He led the Irish delegation at the negotiations that produced the 1921 Anglo-Irish Treaty, and served as the president of Dáil Éireann from January 1922 until his death that August.
After a short spell in South Africa, Griffith founded and edited the Irish nationalist newspaper The United Irishman in 1899. In 1904, he wrote The Resurrection of Hungary: A Parallel for Ireland, which advocated the withdrawal of Irish members from the Parliament of the United Kingdom and the setting up of the institutions of government at home in Ireland, a policy that became known as Sinn Féin (ourselves). On 28 November 1905, he presented "The Sinn Féin Policy" at the first annual convention of his organisation, the National Council; the occasion is marked as the founding date of the Sinn Féin party. Griffith took over as president of Sinn Féin in 1911, but at that time the organisation was still small.
Griffith was arrested following the Easter Rising of 1916, despite not having taken any part in it.