The Dáil Courts were established in June 1920 by Dáil Éireann as part of its policy of undermining British authority in Ireland during the Anglo-Irish War. The courts were usually informal affairs arbitrated by senior Irish Republican Army or Sinn Féin figures who had moral authority in the area. They filled a vacuum which had been created by the conflict, and succeeded in persuading people who were inclined to fear the IRA's revolutionary nature that an independent Ireland would not affect personal and property rights. During the war, the courts gradually extended their influence across most of the country, usurping the British law courts as the British government lost its moral authority in the eyes of the majority.

The Dáil Courts replaced the Sinn Féin Arbitration Courts, set up in August 1919, which only had jurisdiction in property disputes and had been coming under pressure to hear criminal cases. These had only been fully operational in West Clare. The Dáil Courts were more successful and widespread.

Among the less serious offences dealt with by the courts were "rowdyism", larceny, breaches of the licensing laws, damage to property , abusive language towards women, bank and post-office robberies and assaults. Punishment for these lesser offences varied, including returning any stolen property, restitution, repairing damage, fines, and marooning on an island for a period. Incarceration was not a serious option during the conflict. More serious offences merited exile from Ireland, which increased the workload of some English courts dramatically. Treason, though punishable by death, was not part of the courts' remit.

The laws and precedence were taken from the law that existed in Ireland on the day Dáil Éireann first sat, the 21st of January 1919. It was also possible to cite Brehon, French and Roman law. In some areas where the British military presence was especially strong (such as County Cork), the courts could only meet intermittently. The courts' rulings were enforced by IRA Volunteers, who often viewed them as a distraction from their main task. The courts were important in bringing the IRA further under the authority of the Dáil, which hitherto had been little more than nominal, as some commanders were overly inclined to prize their autonomy.

The war ended with the Truce of 1921, and the Dáil Courts were wound up by the Third Dáil in July 1923, after the formation of the Irish Free State.

Institutions of the Irish Republic (1919-1922)