The Battle of Aughrim (Irish: Cath Eachroma) was the decisive battle of the Williamite War in Ireland. It was fought between the largely Irish Jacobite army loyal to James II and the forces of William III on 12 July 1691 (old style, equivalent to 22 July new style), near the village of Aughrim, County Galway.

The battle was possibly the bloodiest ever fought in the British Isles: 5,000–7,000 people were killed. The Jacobite defeat at Aughrim meant the effective end of James's cause in Ireland, although the city of Limerick held out until the autumn of 1691.