O’Brien’s Bridge or O’Briensbridge is a village in east County Clare, Ireland, on the west bank of the River Shannon. The first bridge across the river here was built in 1506 by Turlough O’Brien, First Earl of Thomond and his brother, the Bishop of Killaloe.

Toirdhealbhach Ua Briain, anglicised Turlough O’Brien, was King of Munster and effectively High King of Ireland. A grandson of Brian Bóruma, Toirdelbach was the son of Tadc mac Briain who was killed in 1023 by his half-brother Donnchad mac Briain.

For the first forty years of his life nothing is known of Toirdelbach. It was not until the 1050s that he found allies in Connacht and in Leinster, particularly the powerful King of Leinster Diarmait mac Maíl na mBó, who would aid his claims to be ruler of Munster. In 1071, Toirdelbach led an army on a raid into the midlands in 1071, and had his soldiers build wooden bridges across the Shannon, likely for military purposes, at Áth Caille (possibly modern O’Briensbridge) and Killaloe.

Five of the arches on the western side of the bridge date from this period. Six arches on the eastern side were replaced by the Shannon Commissioners in 1842. The first arch on the western side was replaced by the present navigation arch when the Shannon Scheme was built downstream in 1925-29.

At the eastern end of today’s 14-arch bridge lies the village of Montpelier in County Limerick.

The ancient river-crossing here is believed to be identical with Áth Caille (meaning “Ford of the Wood”): one of the three fords mentioned in the Triads of Ireland, the others being Áth Clíath (Dublin) and Áth Lúain (Athlone).