The Williamite War in Ireland, also known as the Jacobite War in Ireland and in Ireland as Cogadh an Dá Rí or The War of the Two Kings, is the opening conflict following the deposition of King James II in 1688 when he attempts to regain the throne of his Three Kingdoms from his daughter Mary II who has replaced him jointly with her husband William of Orange.

It influences the Jacobite Rising in Scotland led by Viscount Dundee which startesat about the same time.

While William successfully defeats Jacobitism in Ireland and subsequent Jacobite Risings are confined to Scotland and England, the War is to have a lasting effect on Ireland, confirming British and Protestant rule over the country for over a century.

The iconic Williamite victories of the Siege of Derry and the Battle of the Boyne are still celebrated by the Unionist community in Northern Ireland today.