The Irish War of Independence (January 1919 - July 1921) was a guerrilla campaign mounted against the British government in Ireland by the Irish Republican Army (IRA) under the First Dáil, the Irish parliament created in 1919 by a majority of Irish MPs.

It is also known as the Anglo-Irish War or the Tan War or Cogadh na Saoirse or Cogadh Angla-Éireannach in Irish. The IRA that fought in this conflict is often referred to as the Old IRA to distinguish it from later organizations that used the same name.