Brian Boru's Fort, Ring fort on River Shannon near Killaloe, Ireland

Brian Boru's Fort is a circular earthen ringfort immediately north of Killaloe, on the west bank of the River Shannon where it opens into Lough Derg. The mound measures about 70 m in diameter. Excavation in 1961 found postholes of a rectangular wooden building about 4 m by 2.5 m with a central hearth and a paved entryway, set perpendicular to the bank.

Dáithí Ó hÓgáin identified the site as Brian Boru's birthplace or childhood home; as an adult he was based at Kincora, further south. The ringfort was built in the eleventh century and may have stood until 1116, when Tairrdelbach Ua Conchobair's men defeated the Ua Briain and destroyed Kincora. In 1207 the Normans tried to build a motte and bailey here but were driven off; Geoffrey de Marisco built a castle at Killaloe instead in 1216.

The name Béal Bórumha means "mouth of cattle tribute", possibly referring to a fording point where the Dál gCais paid or received such tributes. The site appears in Morgan Llywelyn's 1990 novel Brian Boru: Emperor of the Irish, which won a Bisto Award.

The fort sits roughly 1 mile north of Killaloe village and provides views across Lough Derg and the Shannon crossing point. The banks are easily accessible on foot and offer good vantage points for taking in the surrounding landscape.

Excavations in the 1960s revealed an earlier structure lying beneath what visitors see today, showing that the site was occupied in earlier periods. Archaeologists also discovered Viking-era coins from the 11th century, suggesting links to Norse trade or settlement.