The First Dáil was Dáil Éireann as it convened from 1919 to 1921. It was the first meeting of the unicameral parliament of the revolutionary Irish Republic. In the December 1918 election to the Parliament of the United Kingdom, the Irish republican party Sinn Féin won a landslide victory in Ireland. In line with their manifesto, its MPs refused to take their seats, and on 21 January 1919 they founded a separate parliament in Dublin called Dáil Éireann. They declared Irish independence, ratifying the Proclamation of the Irish Republic that had been issued in the 1916 Easter Rising, and adopted a provisional constitution.

Dáil Éireann, also called the Revolutionary Dáil, was the revolutionary, unicameral parliament of the Irish Republic from 1919 to 1922. The Dáil was first formed on 21 January 1919 in Dublin by 69 Sinn Féin MPs elected in the 1918 United Kingdom general election, who had won 73 seats of the 105 seats in Ireland, with four party candidates elected for two constituencies. Their manifesto refused to recognise the British parliament at Westminster and instead established an independent legislature in Dublin. The convention of the First Dáil coincided with the beginning of the War of Independence.